video: test: Split copy frame buffer check into a function

video: test: Split copy frame buffer check into a function

While checking frame buffer contents, the video tests also check if the
copy frame buffer contents match the main frame buffer. To test if only
the modified regions are updated after a sync, we will need to create
situations where the two are mismatched. Split this check into another
function that we can skip calling, since we won't want it to error on
those mismatched cases.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/u-boot/20230821135111.3558478-2-alpernebiyasak@gmail.com/