[InstCombine] Add mul with negated power of 2 constant to canEvaluateShifted.

If we are right shifting a multiply by a negated power of 2 where
the power of 2 is the same as the shift amount, we can replace with
a negate followed by an And.

New tests have not been committed yet but the patch shows the diffs.
Let me know if you want any changes or additional tests.

Differential Revision: https://reviews.llvm.org/D130103