fs/fs-writeback: This trace event causes a ICE in the mentioned compiler

$ arm-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=arm-eabi-gcc
COLLECT_LTO_WRAPPER=/home/showp1984/WORK/toolchain/android-toolchain-eabi/bin/../libexec/gcc/arm-eabi/4.7.2/lto-wrapper
Target: arm-eabi
Configured with: /mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-src/gcc-linaro-4.7-2012.09/configure --prefix=/tmp/android-toolchain-eabi --host=x86_64-linux-gnu --build=x86_64-linux-gnu --with-gnu-as --with-gnu-ld --enable-languages=c,c++ --with-gmp=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-mpfr=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-mpc=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-cloog=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-ppl=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --disable-ppl-version-check --disable-cloog-version-check --enable-cloog-backend=isl --with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm' --disable-libssp --disable-nls --disable-libmudflap --disable-shared --disable-sjlj-exceptions --disable-libquadmath --disable-libitm --disable-libatomic --with-float=soft --with-fpu=vfp --with-arch=armv5te --enable-target-optspace --prefix=/tmp/android-toolchain-eabi --disable-docs --disable-nls --with-gcc-version=linaro-4.7-2012.09 --with-binutils-version=2.23.51.0.3 --with-gmp-version=5.0.5 --with-mpfr-version=3.1.1 --with-mpc-version=1.0 --target=arm-eabi --enable-threads --enable-tls --disable-libgomp --disable-libstdc__-v3 --disable-libitm --disable-libatomic
Thread model: single
gcc version 4.7.2 20120910 (prerelease) (Linaro GCC 4.7-2012.09)

ICE:
  CC      fs/fs-writeback.o
fs/fs-writeback.c: In function 'bdi_writeback_thread':
fs/fs-writeback.c:685:1: internal compiler error: in push_minipool_fix, at config/arm/arm.c:13180
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
make[1]: *** [fs/fs-writeback.o] Error 1
make: *** [fs] Error 2

Since we don't need traces, just comment it out for now.

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>
fix ICE in fs/fs-writeback.c with gcc4.7:

fs/fs-writeback.c: In function 'bdi_writeback_thread':
fs/fs-writeback.c:993:1: internal compiler error: in push_minipool_fix, at config/arm/arm.c:13180
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
make[1]: *** [fs/fs-writeback.o] Error 1
make: *** [fs] Error 2

$ arm-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=/home/showp1984/WORK/toolchain/android-toolchain-eabi/bin/arm-eabi-gcc
COLLECT_LTO_WRAPPER=/home/showp1984/WORK/toolchain/android-toolchain-eabi/bin/../libexec/gcc/arm-eabi/4.7.2/lto-wrapper
Target: arm-eabi
Configured with: /mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-src/gcc-linaro-4.7-2012.09/configure --prefix=/tmp/android-toolchain-eabi --host=x86_64-linux-gnu --build=x86_64-linux-gnu --with-gnu-as --with-gnu-ld --enable-languages=c,c++ --with-gmp=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-mpfr=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-mpc=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-cloog=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --with-ppl=/mnt/jenkins/workspace/linaro-android_toolchain-4.7-2012.09/build/objdir/temp-install --disable-ppl-version-check --disable-cloog-version-check --enable-cloog-backend=isl --with-host-libstdcxx='-static-libgcc -Wl,-Bstatic,-lstdc++,-Bdynamic -lm' --disable-libssp --disable-nls --disable-libmudflap --disable-shared --disable-sjlj-exceptions --disable-libquadmath --disable-libitm --disable-libatomic --with-float=soft --with-fpu=vfp --with-arch=armv5te --enable-target-optspace --prefix=/tmp/android-toolchain-eabi --disable-docs --disable-nls --with-gcc-version=linaro-4.7-2012.09 --with-binutils-version=2.23.51.0.3 --with-gmp-version=5.0.5 --with-mpfr-version=3.1.1 --with-mpc-version=1.0 --target=arm-eabi --enable-threads --enable-tls --disable-libgomp --disable-libstdc__-v3 --disable-libitm --disable-libatomic
Thread model: single
gcc version 4.7.2 20120910 (prerelease) (Linaro GCC 4.7-2012.09)

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>