MIPS: add mips64r5 generic architecture variant

-march=mips64r5 support started from GCC-5, so disable previous versions
when the CPU is R5.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
2 files changed