regulator: Add snapshot of qpnp-amoled regulator driver

Add QPNP AMOLED regulator driver to configure triple power supply
(OLED, AB & IBB) that is used in AMOLED panels.

This is a snapshot of the driver taken from msm-4.19 as of
'commit <18fb0f227fcdcd3i92a380533b454fdc629625327> ("Merge power:
supply: qcom: Initial version driver for SMB1398 charger")'.

Change-Id: Iefa5d27f781af36d42e0a14ac77b2537a19ea596
Signed-off-by: Shyam Kumar Thella <sthella@codeaurora.org>