regulator: axp20x: Fix reference cout leak

Decrements the reference count of device node and its child node.

Fixes: dfe7a1b0 ("regulator: AXP20x: Add support for regulators subsystem")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Link: https://lore.kernel.org/r/20210120123313.107640-1-bianpan2016@163.com


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