drm/simpledrm: Support the XB24/AB24 format

Add XB24 and AB24 to the list of supported formats. The format helpers
support conversion to these formats and they are documented in the
simple-framebuffer device tree bindings.
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230120173103.4002342-8-thierry.reding@gmail.com

include/linux/platform_data/simplefb.h

@@ -22,6 +22,7 @@
 	{ "r8g8b8", 24, {16, 8}, {8, 8}, {0, 8}, {0, 0}, DRM_FORMAT_RGB888 }, \
 	{ "x8r8g8b8", 32, {16, 8}, {8, 8}, {0, 8}, {0, 0}, DRM_FORMAT_XRGB8888 }, \
 	{ "a8r8g8b8", 32, {16, 8}, {8, 8}, {0, 8}, {24, 8}, DRM_FORMAT_ARGB8888 }, \
+	{ "x8b8g8r8", 32, {0, 8}, {8, 8}, {16, 8}, {0, 0}, DRM_FORMAT_XBGR8888 }, \
 	{ "a8b8g8r8", 32, {0, 8}, {8, 8}, {16, 8}, {24, 8}, DRM_FORMAT_ABGR8888 }, \
 	{ "x2r10g10b10", 32, {20, 10}, {10, 10}, {0, 10}, {0, 0}, DRM_FORMAT_XRGB2101010 }, \
 	{ "a2r10g10b10", 32, {20, 10}, {10, 10}, {0, 10}, {30, 2}, DRM_FORMAT_ARGB2101010 }, \