ARM refactor am6offset usage for VLD1.

Split am6offset into fixed and register offset variants so the instruction
encodings are explicit rather than relying an a magic reg0 marker.
Needed to being able to parse these.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142853 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed