backlight: Do not include <linux/fb.h> in header file

The backlight interfaces don't require anything from <linux/fb.h>, so
don't include it.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Link: https://patch.msgid.link/20251013105553.836715-1-tzimmermann@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>

Author: tdz

include/linux/backlight.h

@@ -10,7 +10,6 @@
 #define _LINUX_BACKLIGHT_H
 
 #include <linux/device.h>
-#include <linux/fb.h>
 #include <linux/mutex.h>
 #include <linux/types.h>