power: smb5: Configure termination current thresholds

Add support to configure charge termination upper and lower thresholds
for ADC comparator. Since the charge termination can be based off analog
comparator in the charger peripheral, add support to configure the type
of source for termination.

Also expose the configured charge termination threshold (upper
in case of ADC comparator) through CHARGE_TERM_CURRENT property.

CRs-Fixed: 2255712
Change-Id: I5596877a9954b5a5e3c36e3f0b2c5159e03f6e61
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>