ARM vldm and vstm VFP instructions can take a data type suffix.

It's ignored by the assembler when present, but is legal syntax. Other
instructions have something similar, but for some mnemonics it's
only sometimes not significant, so this quick check in the parser will
need refactored into something more robust soon-ish. This gets some
basics working in the meantime.

Partial for rdar://10435264

llvm-svn: 144422