panfrost: Don't copy resources if replaced

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: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19361>
(cherry picked from commit 0b26a9f773956fc00a77b0d4a7aafee5795ce935)