regulator: Fix compiler warnings

gcc 6.1.1 triggers a few compiler warnings for uninitalized
variables and an incorrect return type for a inline function.

Fixes: ee1e5e10 ("regulator: Addsnapshot of qpnp-labibb regulator driver")
Change-Id: Ic0dedbada0e3d4984fbf134ca0969106751a2524
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>