[LegalizeTypes] Fix bug in expensive checks verification

With a fix for an expensive checks build failure exposed by new RISC-V tests.
Something about expanding two rotates in type legalization caused a change
in the remapping tables that the expensive checks verifying wasn't expecting.
See comment in the code for how it was fixed.

Tests came from this commit that exposed the bug
[RISCV] Add test cases showing failure to remove mask on rotate amounts.

If the masking AND has multiple users we fail to remove it.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D126036