st/mesa: flush bitmap cache before CopyImageSubData

Found by inspection.

Cc: 11.2 12.0 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit f9ddd52317caf14a21ec7c040fd4bb944f9842e4)
1 file changed