MIPS: Support swaps between 128-bit locations

Add support for swaps between two SIMDStackSlots, two
VectorRegisters (extended FpuRegister) and between a
SIMDStackSlot and a VectorRegister.

This fixes test 623-checker-loop-regressions for
MIPS64R6 and MIPS32R6.

Test: ./testrunner.py --optimizing --target in QEMU (MIPS64R6)
Test: ./testrunner.py --optimizing --target in QEMU (MIPS32R6)

Change-Id: I36aa209f79790fb6c08b9a171f810769a6b40afc
6 files changed