Added sub-formats to the NeonI/NeonXI instructions to further refine the NEONFrm

Added sub-formats to the NeonI/NeonXI instructions to further refine the NEONFrm
instructions to help disassembly.

We also changed the output of the addressing modes to omit the '+' from the
assembler syntax #+/-<imm> or +/-<Rm>.  See, for example, A8.6.57/58/60.

And modified test cases to not expect '+' in +reg or #+num.  For example,

; CHECK:       ldr.w	r9, [r7, #28]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98745 91177308-0d34-0410-b5e6-96231b3b80d8