[InstCombine] Do not simplify lshr/shl arg if it is part of a rotate pattern

fshl/fshr having first two arguments as same gets lowered to target
specific rotate. But based on the uses, one of the arguments can get
simplified resulting in different arguments performing equivalent
operation.

This patch prevents the simplification of the arguments of lshr/shl if
they are part of fshl pattern.

Closes https://github.com/llvm/llvm-project/pull/73441.