[CodeGenPrepare] Avoid out-of-bounds shift

AddressingModeMatcher::matchOperationAddr may attempt to shift a
variable by the same amount of steps as found in the IR in a SHL
instruction. This was done without considering that there could be
undefined behavior in the IR, so the shift performed when compiling
could end up having undefined behavior as well.

This patch avoid UB in the codegenprepare by making sure that we
limit the shift amount used, in a similar way as already being done
in CodeGenPrepare::optimizeLoadExt.

Differential Revision: https://reviews.llvm.org/D118602