drm/mediatek: only announce AFBC if really supported

Currently even the SoC's OVL does not declare the support of AFBC, AFBC
is still announced to the userspace within the IN_FORMATS blob, which
breaks modern Wayland compositors like KWin Wayland and others.

Gate passing modifiers to drm_universal_plane_init() behind querying the
driver of the hardware block for AFBC support.

Fixes: c410fa9b ("drm/mediatek: Add AFBC support to Mediatek DRM driver")
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: CK Hu <ck.hu@medaitek.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20250531121140.387661-1-uwu@icenowy.me/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>