drm/panel: sitronix-st7789v: remove unused constants

ST7789V_COLMOD_RGB_FMT_18BITS and ST7789V_COLMOD_CTRL_FMT_18BITS
are unused in favour of MIPI_DCS_PIXEL_FMT_18BIT, remove them.
Reviewed-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230714013756.1546769-5-sre@kernel.org

drivers/gpu/drm/panel/panel-sitronix-st7789v.c

@@ -15,9 +15,6 @@
 #include <drm/drm_modes.h>
 #include <drm/drm_panel.h>
 
-#define ST7789V_COLMOD_RGB_FMT_18BITS		(6 << 4)
-#define ST7789V_COLMOD_CTRL_FMT_18BITS		(6 << 0)
-
 #define ST7789V_RAMCTRL_CMD		0xb0
 #define ST7789V_RAMCTRL_RM_RGB			BIT(4)
 #define ST7789V_RAMCTRL_DM_RGB			BIT(0)