regulator: msm_gfx_ldo: fix null pointer dereference

Fix a possible null dereference after a runtime memory
allocation made for volt_adjust local variable.

CRs-Fixed: 1106624
Change-Id: I45eedc24e98dede75e7e4bf1374f582d95c3e9b2
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>