power: supply: mt6360_charger: add MT6360 charger support

Add basic support for the battery charger for MT6360 PMIC

Signed-off-by: Gene Chen <gene_chen@richtek.com>
Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>