Fix suffix handling for parsing and printing of cvtsi2ss, cvtsi2sd, cvtss2si, cvttss2si, cvtsd2si, and cvttsd2si to match gas behavior.

cvtsi2* should parse with an 'l' or 'q' suffix or no suffix at all. No suffix should be treated the same as 'l' suffix. Printing should always print a suffix. Previously we didn't parse or print an 'l' suffix.
cvtt*2si/cvt*2si should parse with an 'l' or 'q' suffix or not suffix at all. No suffix should use the destination register size to choose encoding. Printing should not print a suffix.

Original 'l' suffix issue with cvtsi2* pointed out by Michael Kuperstein.

llvm-svn: 171668