drm/panel: use mipi_dsi_dcs_write_buffer where possible

A few of the new panels create a local macro wrapping around
mipi_dsi_dcs_write. At the same time, they don't really care about the
command/payload split.

mipi_dsi_dcs_write does a kmalloc/memcpy/kfree for payload > 7 bytes.
Avoid that all together by using the _buffer function.

Aside:
panel-xinpeng-xpp055c272.c calls its wrapper "generic" although it
should be "dcs". But that for another day/patch.

Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200505160329.2976059-2-emil.l.velikov@gmail.com

drivers/gpu/drm/panel/panel-elida-kd35t133.c

@@ -52,9 +52,9 @@ static inline struct kd35t133 *panel_to_kd35t133(struct drm_panel *panel)
 }
 
 #define dsi_dcs_write_seq(dsi, cmd, seq...) do {			\
-		static const u8 d[] = { seq };				\
+		static const u8 b[] = { cmd, seq };			\
 		int ret;						\
-		ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d));	\
+		ret = mipi_dsi_dcs_write_buffer(dsi, b, ARRAY_SIZE(b));	\
 		if (ret < 0)						\
 			return ret;					\
 	} while (0)

drivers/gpu/drm/panel/panel-leadtek-ltk050h3146w.c

@@ -246,9 +246,9 @@ struct ltk050h3146w *panel_to_ltk050h3146w(struct drm_panel *panel)
 }
 
 #define dsi_dcs_write_seq(dsi, cmd, seq...) do {			\
-		static const u8 d[] = { seq };				\
+		static const u8 b[] = { cmd, seq };			\
 		int ret;						\
-		ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d));	\
+		ret = mipi_dsi_dcs_write_buffer(dsi, b, ARRAY_SIZE(b));	\
 		if (ret < 0)						\
 			return ret;					\
 	} while (0)

drivers/gpu/drm/panel/panel-xinpeng-xpp055c272.c

@@ -62,9 +62,9 @@ static inline struct xpp055c272 *panel_to_xpp055c272(struct drm_panel *panel)
 }
 
 #define dsi_generic_write_seq(dsi, cmd, seq...) do {			\
-		static const u8 d[] = { seq };				\
+		static const u8 b[] = { cmd, seq };			\
 		int ret;						\
-		ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d));	\
+		ret = mipi_dsi_dcs_write_buffer(dsi, b, ARRAY_SIZE(b));	\
 		if (ret < 0)						\
 			return ret;					\
 	} while (0)