[x86] Prevent llvm.x86.cmp.ps/pd/ss/sd from being selected with bad immediates. The frontend now checks this when the builtin is used. This will allow the instruction printer to not have to deal with invalid immediates on these instructions.
[x86] Assert on invalid immediates in the instruction printer for cmp.ps/pd/ss/sd instead of truncating the immediate. The assembly parser and instruction selection shouldn't generate invalid immediates.