ARM & AArch64: convert asm tests to LLVM IR and restrict optimizations.

ARM & AArch64: convert asm tests to LLVM IR and restrict optimizations.

This is mostly a one-time autoconversion of tests that checked assembly after
"-Owhatever" compiles to only run "opt -mem2reg" and check the assembly. This
should make them much more stable to changes in LLVM so they won't break on
unrelated changes.

"opt -mem2reg" is a compromise designed to increase the readability of tests
that check dataflow, while minimizing dependency on LLVM. Hopefully mem2reg is
stable enough that no surpises will come along.

Should address http://llvm.org/PR26815.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@263048 91177308-0d34-0410-b5e6-96231b3b80d8