led: led-class: Read max-brightness from devicetree

Normally, the maximum brightness is determined by the hardware, and this
property is not required. This property is used to set a software limit.
It could happen that an LED is made so bright that it gets damaged or
causes damage due to restrictions in a specific system, such as mounting
conditions.
Note that this flag is mainly used for PWM-LEDs, where it is not possible
to map brightness to current. Drivers for other controllers should use
led-max-microamp.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Astrid Rost <astrid.rost@axis.com>
Acked-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Link: https://lore.kernel.org/r/20230703130313.548519-3-astrid.rost@axis.com


Signed-off-by: Lee Jones <lee@kernel.org>