mfd: axp20x: Convert to use Maple Tree register cache

mfd: axp20x: 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: wangkaiyuan <wangkaiyuan@inspur.com>
Link: https://lore.kernel.org/r/20240429024547.27724-1-wangkaiyuan@inspur.com
Signed-off-by: Lee Jones <lee@kernel.org>