The BenQ GW2765 reports that it supports higher (> 8) bpc modes, but
when trying to set them we end up with a black screen. So, limit it to 8
bpc modes.

Cc: stable@vger.kernel.org # 6.5+
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2610Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231012184927.133137-1-hamza.mahfooz@amd.com