regulator: Add qpnp-amoled regulator

Add QPNP AMOLED regulator to configure triple power supply
(OLEDB, AB, IBB) that is used in AMOLED panels. Currently this
supports only PM8150A AOD mode configuration.

Change-Id: I6c5c36d9ceb0040c73faef0a7ec8637b4acf77d4
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>