regulator: Add QTI LCDB regulator driver

Add snapshot of QTI LCDB regulator driver that helps with
controlling display bias voltage rails for LCD panels.

This snapshot is taken as of msm-4.14
commit 9bb584ae ("msm/sde/rotator: Add rev checks for sdmmagpie").

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

Change-Id: Ia3510bb69cd36579329d5ded3abfc6991458eb35
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>