panfrost: Don't copy resources if replaced
If a synchronized transfer_map is going to overwrite an entire resource, there's no need to memcpy in the original contents ahead-of-time. This memcpy is particularly bad for large buffers where it's copying WC->WC, although that could be mitigated with threaded_context's cpu_storage in the future if needed. Prevents a performance regression in glmark2's buffer scenes from the next patch, hence the Cc. Cc: mesa-stable Signed-off-by:Alyssa Rosenzweig <alyssa@collabora.com> Part-of: <mesa/mesa!19361>