power: smb1360: Add OTG FET and FG-gain control support

Add support to control OTG FET and current gain when
charger is configured in OTG mode. This allows a max
battery current of 4.5A during OTG.

CRs-Fixed: 746025
Change-Id: Id64dd927fd40d3bd481e3adff6bc527e8cc87459
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>