[ValueTracking] add range limits for ctpop
As discussed in D89952,
instcombine can sometimes find a way to reduce similar patterns,
but it is incomplete.
InstSimplify uses the computeConstantRange() ValueTracking analysis
via simplifyICmpWithConstant(), so we just need to fill in the max
value of ctpop to process any "icmp pred ctpop(X), C" pattern (the
min value is initialized to zero automatically).
Differential Revision: https://reviews.llvm.org/D89976