drm/mediatek: Remove mt8192 display rdma compatible

The compatible “mediatek,mt8192-disp-rdma” is being used for reading
the data into DMA for back-end panel driver in mt8192 but there is
no difference between mt8183 and mt8192 in rdma driver.

Remove compatible “mediatek,mt8192-disp-rdma” from the driver and
should use “mediatek,mt8183-disp-rdma” as fallback in 8192 DTS
according to the mediatek,rdma.yaml.

Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20220701090547.21429-2-allen-kh.cheng@mediatek.com/


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