[FastISel][AArch64] Add target-specific lowering for logical operations.

This change adds support for immediate and shift-left folding into logical
operations.

This fixes rdar://problem/18223183.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217118 91177308-0d34-0410-b5e6-96231b3b80d8
[FastISel][AArch64] Cleanup and simplify 'fastSelectInstruction'. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217119 91177308-0d34-0410-b5e6-96231b3b80d8