[InstCombine] Add transforms for `(rem (shl Y, X), (shl Z, X))`

This is just filling in a missing case from D144225.

We treat `(shl Y, X)` and `(shl Z, X)` as `(mul Z, 1 << X)` and `(mul
Y, 1 << X)` then reuse the same transformations that already exist.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D147108