Fix LDRH emitter bug, use STMIA where possible

This fixes the issue with LDRH for me in Dissidia.  By the way, disarm seems to mishandle LDRH/LDRB/etc.

Unfortunately, the Lunar bug still persists.  It goes away if I don't jit Jit_PosS16Through (although I'm not 100% sure that it's in that func, or just another thing I'm disabling as well.)  I was hoping it'd be the same issue because of LDRSH.

Armjit was never using this form of LDRH/etc. afaict.

-[Unknown]