regulator: Add snapshot of qpnp-labibb regulator driver

Add snapshot of QPNP LABIBB regulator driver that supports controlling
the display bias voltage rails on QTI PMICs that powers up LCD or
AMOLED 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: Iad4f4721f07ed796f71f8975878f8dcbbb216bc1
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>