Debug info: Remove ARMAsmPrinter::EmitDwarfRegOp(). AsmPrinter can now
scan the register file for sub- and super-registers.
No functionality change intended.

(Tests are updated because the comments in the assembler output are
different.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202416 91177308-0d34-0410-b5e6-96231b3b80d8