[ARM] Add missing memory operands to a bunch of instructions.

This should hopefully lead to minor improvements in code generation, and
more accurate spill/reload comments in assembly.

Also fix isLoadFromStackSlotPostFE/isStoreToStackSlotPostFE so they
don't lead to misleading assembly comments for merged memory operands;
this is technically orthogonal, but in practice the relevant memory
operand lists don't show up without this change.

Differential Revision: https://reviews.llvm.org/D59713

llvm-svn: 356963