regulator: cpr4: add support for aging voltage margin adjustment

Add support for increasing the closed-loop voltage margin over
time based upon the results of aging sensor measurements.  The
aging ring oscillators (ROs) are arranging in pairs such that
one is constantly stressed by the vdd-supply voltage and the
other is never stressed.  The difference between the quotients
measured by these ROs gives an indication of how much the silicon
has aged.

CRs-Fixed: 1025832
Change-Id: I2948c227153569d3c785ea3ac6d75453525db7e1
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>