defconfig: msm: Enable maxim regulator driver for msm8996-auto

Enable Maxim20010 external buck regulator driver to provide the supply
for graphics rail on msm8996-auto boards.

CRs-Fixed: 2062515
Change-Id: I1e70f16c660de6d3d2a8c138a34157538c19f0f1
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>