[ARM] Constrain CMPZ shift combine to a single use

We currently prefer t2CMPrs over t2CMPri when the node contains a shift.
This can introduce more nodes if the shift has multiple uses though, as
value from the shift will be needed anyway, and in the case of a t2CMPri
compared with zero will more readily be removed entirely.

Differential Revision: https://reviews.llvm.org/D101688