This patch implements a few changes related to the Thumb2 M-class MSR instruction:
* better handling of unpredictable encodings,
* recognition of the _g and _nzcvqg variants by the asm parser only if the DSP
extension is available, preferred output of MSR APSR moves with the _<bits>
suffix for v7-M.
Patch by Petr Pavlu.
llvm-svn: 216874
