[MIPS] Add FPU Delay Slot for MIPS1/2/3

MIPS I, II, and III have delay slots for floating point
comparisons and floating point register transfers (mtc1, mfc1).
Currently, these are not taken into account and thus broken code
may be generated on these targets. This patch inserts nops
as necessary, while attempting to leave the current instruction
if it is safe to stay.

The tests in this patch were updated by @sajattack

Patch by @overdrivenpotato (Marko Mijalkovic <marko.mijalkovic97@gmail.com>)

Differential Revision: https://reviews.llvm.org/D115127