[AArch64] Fix assembly string formatting and other coding standard violations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193866 91177308-0d34-0410-b5e6-96231b3b80d8
[AArch64] Simplify a few of the instruction patterns. No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193867 91177308-0d34-0410-b5e6-96231b3b80d8