backlight: led_bl: Include <linux/of.h>

Include <linux/of.h> to declare struct of_count_phandle_with_args().
Avoids dependency on backlight header to include it.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: "Daniel Thompson (RISCstar)" <danielt@kernel.org>
Link: https://lore.kernel.org/r/20250715122643.137027-13-tzimmermann@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>

Author: tdz

drivers/video/backlight/led_bl.c

@@ -9,6 +9,7 @@
 #include <linux/backlight.h>
 #include <linux/leds.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 
 struct led_bl_data {