1. Introduce a new TargetOperandInfo::getRegClass() helper method

   and convert code to using it, instead of having lots of things
   poke the isLookupPtrRegClass() method directly.

2. Make PointerLikeRegClass contain a 'kind' int, and store it in
   the existing regclass field of TargetOperandInfo when the
   isLookupPtrRegClass() predicate is set.  Make getRegClass pass
   this into TargetRegisterInfo::getPointerRegClass(), allowing
   targets to have multiple ptr_rc things.

llvm-svn: 77504