[IndVars] Add check of loop invariant for indirect use

We usually only check direct use instruction of IV, while the
bitcast of 'ptrtoint ptr to i64' doesn't affect the result, so go
a step further.
Fix https://github.com/llvm/llvm-project/issues/59633.

Reviewed By: markoshorro
Differential Revision: https://reviews.llvm.org/D151877