backlight: hp680_bl: Do not include <linux/fb.h>

This driver does not require <linux/fb.h>. Remove the include
statement.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/video/backlight/hp680_bl.c

···
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/spinlock.h>
-#include <linux/fb.h>
 #include <linux/backlight.h>
 
 #include <cpu/dac.h>