ARM: dts: msm: Add Maxim regulator node for msm8996

Maxim20010 buck regulator is used to provide the supply for
graphics rail. The programmable output voltage range is from
0.5V to 1.27V in 10mV steps.

CRs-Fixed: 2062515
Change-Id: I50d3fe4c89f412cda2b58b3f1f19086edcf10553
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>