ARM: dts: msm: Add mem-acc-regulator device for 8909

The memory accelerator controls delays while accessing memories, the
delays should be changed according to CPR corner switching.

Add a mem-acc-regulator device node and assign it to mem-acc-supply
property in CPR device node. This make sure that the memory accelerator
can be controlled while changing corners.

Change-Id: I24d8733010a8facd07251fbbdcf03b90e9608e31
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>