build: clean up default cflags handling

- reduce redundancy
- introduce a CPU_TYPE variable for cpu specific options

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38209 3c298f89-4303-0410-b956-a3cf2f4a3e73
build: unify mips target cflags

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38210 3c298f89-4303-0410-b956-a3cf2f4a3e73
build: unify arm target cflags

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38211 3c298f89-4303-0410-b956-a3cf2f4a3e73
build: unify x86 target cflags

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38212 3c298f89-4303-0410-b956-a3cf2f4a3e73
build: unify powerpc target cflags

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38213 3c298f89-4303-0410-b956-a3cf2f4a3e73
build: include the cpu type as part of the toolchain/target directory name

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38214 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel/3.8: add missing config symbols

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38215 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel/3.9: add missing config symbols

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38216 3c298f89-4303-0410-b956-a3cf2f4a3e73