regulator: Add QTI OLEDB regulator driver

Add snapshot of QTI OLEDB regulator driver that helps with
controlling AVDD bias voltage rail for AMOLED panels.

This snapshot is taken as of msm-4.14
commit 9bb584ae3a9d ("msm/sde/rotator: Add rev checks for sdmmagpie").

This change also splits some functions to fix cyclomatic complexity
warnings.

Change-Id: I1237c353b1e6dfc8510566919798606ce37fb76c
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>