mips32/mips64: Fix the problem with VKI_ENOSYS and VKI_EOVERFLOW for mips32/64.

VKI_ENOSYS and VKI_EOVERFLOW don't have the same generic values for mips32/64.
We need to define these values for every Linux arch.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13852 a5019735-40e9-0310-863c-91ae7b9d1cf9