Use named constants instead of integers in call_fext_func() invocations
related to backlight power control in order to more clearly convey the
intent of each call.
Signed-off-by: NMichał Kępień <kernel@kempniu.pl>
Reviewed-by: NJonathan Woithe <jwoithe@just42.net>
Signed-off-by: NDarren Hart (VMware) <dvhart@infradead.org>