remove strings from instructions who are never asmprinted.

remove strings from instructions who are never asmprinted.
All of these "subreg32" modifier instructions are handled
explicitly by the MCInst lowering phase.  If they got to
the asmprinter, they would explode.  They should eventually
be replace with correct use of subregs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84526 91177308-0d34-0410-b5e6-96231b3b80d8