drm/mediatek: Add mediatek-drm plane color encoding info

Add plane color encoding information for color space conversion.
It's a preparation for adding support for mt8195 ovl_adaptor mdp_rdma
csc control.

Signed-off-by: Nancy.Lin <[e-mail]>
Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Tested-by: AngeloGioacchino Del Regno <[e-mail]>
Tested-by: Bo-Chen Chen <[e-mail]>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/[e-mail]/
Signed-off-by: Chun-Kuang Hu <[e-mail]>

drivers/gpu/drm/mediatek/mtk_drm_plane.c

···
 	mtk_plane_state->pending.width = drm_rect_width(&new_state->dst);
 	mtk_plane_state->pending.height = drm_rect_height(&new_state->dst);
 	mtk_plane_state->pending.rotation = new_state->rotation;
+	mtk_plane_state->pending.color_encoding = new_state->color_encoding;
 }
 
 static void mtk_plane_atomic_async_update(struct drm_plane *plane,

drivers/gpu/drm/mediatek/mtk_drm_plane.h

···
 	bool				dirty;
 	bool				async_dirty;
 	bool				async_config;
+	enum drm_color_encoding		color_encoding;
 };
 
 struct mtk_plane_state {