Apply again changes to support ARM memory asm parsing. I removed

Apply again changes to support ARM memory asm parsing. I removed
all LDR/STR changes and left them to a future patch. Passing all
checks now.

- Implement asm parsing support for LDRT, LDRBT, STRT, STRBT and
  fix the encoding wherever is possible.
- Add a new encoding bit to describe the index mode used and teach
  printAddrMode2Operand to check by the addressing mode which index
  mode to print.
- Testcases

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128689 91177308-0d34-0410-b5e6-96231b3b80d8