Generalize sysfs master_fader since their implementation is the same across
some lp55xx based LED driver.
Suggested-by: Lee Jones <lee@kernel.org>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20240626160027.19703-18-ansuelsmth@gmail.comSigned-off-by: Lee Jones <lee@kernel.org>