[AMDGPU] isRenamable fixes to support copy forwarding

Mark more opcodes as hasExtraSrcRegAllocReq so that their operands will
be marked as not renamable, to avoid copy forwarding violating the
constraint that only one operand may use the constant bus.

These changes fix a few mis-compiles when copy forwarding is enabled in
MachineCopyPropagation by D41835 (and were reviewed as part of that change).

llvm-svn: 323794