regulator: mem-acc-regulator: Add ACC custom data configuration

Some targets need specific data to be configured into L1 and L2
CUSTOM_ACC registers across APC corner switch. Add support to
pass custom register addresses and configuration data through
device tree.

CRs-Fixed: 715818
Change-Id: I96245382d3980f96ec7a1eea5d680284939ae925
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>