Erase gpu.memcpy op when only uses of dest are
the memcpy op in question, its allocation and deallocation
ops.
Reviewed By: bondhugula, csigg
Differential Revision: https://reviews.llvm.org/D124257
These properties were useful for a few things before traits had a better integration story, but don't really carry their weight well these days. Most of these properties are already checked via traits in most of the code. It is better to align the system around traits, and improve the performance/cost of traits in general.
Differential Revision: https://reviews.llvm.org/D96088