leds: qpnp-flash-v2: Add support for QPNP flash v2 LED driver

QPNP Flash v2 LED driver supports the flash LED peripheral on
QTI PMICs like PMI8998, PM8150L and their derivatives to support
camera flash operation.

This is taken as a snapshot from msm-4.14 kernel
'commit 9bb584ae ("msm/sde/rotator: Add rev checks for sdmmagpie")'

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

Change-Id: I168b1e3e5ce62852f37ee2653aada90f2a75e2ec
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>