mips32: Fpu guest registers are ULong and the initial values need to be
extended.

Because we are supporting both big and little endian mips32 we need to
make sure that the initial values for the fpu registers are the same for both
endian.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2827 8f6e269a-dfd6-0310-a8e1-e2731360e62c