target/mips: MXU: Add handlers for logic instructions

target/mips: MXU: Add handlers for logic instructions

Add translation handlers for four logic MXU instructions.

It should be noted that there is an error in MXU documentation (dated
June 2017) regarding opcodes for this group of instructions. This was
confirmed by running tests on hardware, and also by looking up other
related public source trees (binutils, Android NDK). In initial MXU
patches to QEMU, opcodes for MXU logic instructions were created to
be in accordance with the MXU documentation, therefore the error from
was propagated. This patch corrects that, changing the involved code.
Besides that, as MXU was designed and implemented only for 32-bit
CPUs, corresponding preprosessor conditions were added around MXU
code, which allows more flexible implementation of MXU handlers.

Reviewed-by: Stefan Markovic <smarkovic@wavecomp.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>