backlight: Add missing MODULE_DESCRIPTION() macros

With ARCH=x86, make allmodconfig && make W=1 C=1 reports:

 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/video/backlight/platform_lcd.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/video/backlight/rt4831-backlight.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240612-md-drivers-video-backlight-v1-1-f4ca1beb36cc@quicinc.comSigned-off-by: Lee Jones <lee@kernel.org>

drivers/video/backlight/platform_lcd.c

@@ -143,5 +143,6 @@ static struct platform_driver platform_lcd_driver = {
 module_platform_driver(platform_lcd_driver);
 
 MODULE_AUTHOR("Ben Dooks <ben-linux@fluff.org>");
+MODULE_DESCRIPTION("Generic platform-device LCD power control interface");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:platform-lcd");

drivers/video/backlight/rt4831-backlight.c

@@ -229,4 +229,5 @@ static struct platform_driver rt4831_bl_driver = {
 module_platform_driver(rt4831_bl_driver);
 
 MODULE_AUTHOR("ChiYuan Huang <cy_huang@richtek.com>");
+MODULE_DESCRIPTION("Richtek RT4831 Backlight Driver");
 MODULE_LICENSE("GPL v2");