drm/stm: ltdc: add support of ycbcr pixel formats

This patch adds the following YCbCr input pixel formats on the latest
LTDC hardware version:

1 plane  (co-planar)  : YUYV, YVYU, UYVY, VYUY
2 planes (semi-planar): NV12, NV21
3 planes (full-planar): YU12=I420=DRM YUV420, YV12=DRM YVU420
Signed-off-by: Yannick Fertre <yannick.fertre@foss.st.com>
Acked-by: Philippe Cornu <philippe.cornu@foss.st.com>
Reviewed-by: Philippe Cornu <philippe.cornu@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215214843.20703-1-yannick.fertre@foss.st.com

drivers/gpu/drm/stm/ltdc.h

@@ -24,6 +24,7 @@ struct ltdc_caps {
 	bool non_alpha_only_l1; /* non-native no-alpha formats on layer 1 */
 	int pad_max_freq_hz;	/* max frequency supported by pad */
 	int nb_irq;		/* number of hardware interrupts */
+	bool ycbcr_input;	/* ycbcr input converter supported */
 	bool ycbcr_output;	/* ycbcr output converter supported */
 	bool plane_reg_shadow;	/* plane shadow registers ability */
 };