leds: pwm: Add optional DT property default-brightness

When probing if default LED state is on then default brightness will be
applied instead of max brightness.

Signed-off-by: George Stark <gnstark@salutedevices.com>
Link: https://lore.kernel.org/r/20241105185006.1380166-3-gnstark@salutedevices.com


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