[InstCombine] Transform (icmp eq/ne rotate(X,AX),rotate(Y,AY)) -> (icmp eq/ne rotate(Y,AX-AY))

Only do so if we don't create more instructions, so either both
rotates have one use or one of the rotates has one use and both `AX`
and `AY` are constant.
Proof: https://alive2.llvm.org/ce/z/rVmJgz

Differential Revision: https://reviews.llvm.org/D152348