radv: fix bpe for the stencil aspect of depth/stencil copies on transfer queue

Using the bpe of depth+stencil when copying the stencil aspect only
doesn't work.

Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34143>
5 files changed