Revert "[AArch64] Simplify/refactor code to ease code review. NFC."

This reverts commit r245443, as it broke AArch64 test-suite tramp3d
with an assert "Reg && "Null register has no regunits".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245455 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed