drm/mediatek: mtk_dpi: Support AFIFO 1T1P output and conversion

drm/mediatek: mtk_dpi: Support AFIFO 1T1P output and conversion

On some SoCs, like MT8195 and MT8188, the DPI's FIFO controller
(afifo) supports outputting either one or two pixels per round
regardless of the input being 1T1P or 1T2P.

Add a `output_1pixel` member to struct mtk_dpi_conf which, if
set, will enable outputting one pixel per clock.

In case the input is two pixel per clock (1T2P), the AFIFO HW
will automatically (and internally) convert it to 1T1P.

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20250217154836.108895-9-angelogioacchino.delregno@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>