regulator: rpi-panel-attiny: 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: Bo Liu <liubo03@inspur.com>
Link: https://msgid.link/r/20240320085740.4604-14-liubo03@inspur.com


Signed-off-by: Mark Brown <broonie@kernel.org>