regulator: mem-acc: Add support for multi register configuration

Some targets require sequence of multi register configuration
during corner switch. Add driver support to define and program
the required register configuration sequence.

CRs-Fixed: 927184
Change-Id: I7bc2aea8d194bf4c7f8e3b2d303c4d3477df47fa
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>