[RS4GC] Prune inputs of BDV if they are BDV themselves

Don't check whether an input of BDV can be pruned if the input
is the BDV itself. BDV is present in the states map, so in case
the input is the BDV itself, we'd return false. So explicitly check this case.

Differential Revision: https://reviews.llvm.org/D123846