leds: lm392x: Convert to use maple tree register cache

leds: lm392x: Convert to use maple tree register cache

The maple tree register cache is based on a much more modern data structure
than the rbtree cache and makes optimisation choices which are probably
more appropriate for modern systems than those made by the rbtree cache.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230929-leds-maple-v1-3-ba5f9dcb1e75@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>