Fix a bug in setjmp for MIPS o32/o64 FPXX/FP64

Fix a bug in setjmp for MIPS o32/o64 FPXX/FP64

It seems there is a swapped logic in one of the subcases of
setjmp.S for MIPS: when the FPU registers are 64-bit within
a 32-bit aligned jmp_buf, the code realigns the pointers
before doing 64-bit writes, but the branch logic is swapped:
we must avoid the address adjustement when bit 2 is zero
(that is, the address is already 8-byte aligned).

This always triggers an address error when run, as tested
on a MIPS VR4300 with O64 ABI.