leds: qpnp-flash-v2: Add support for bharger flash

PMI632 flash is driven by the charger in reverse boost
(bharger) mode instead of the BoB regulator. Add the
necessary changes to support the same.

Change-Id: I9166f470f2fdffb12f1c90b1758f606ead2f131a
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>