power: qpnp-qg: Add support for SMB-sensing for SMB1395/6

SMB1395/6 charger has the ability to report the
charge current via IIN_SNS lines to QGauge
(on ISNS_SMB pins). Add support to enable this
SMB-sensing at runtime based on the status of
SMB1395/6.

The DT property 'qcom,use-cp-iin-sns' enables the feature.

Change-Id: I742a7950f9fc53f17cb6f210f2b7f06ade842012
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>