msm: cpr: Modify voltage step_size for 8625q

The external buck regulator is used for driving power supply for
apps core in 8625q. The voltage step size of external buck regulator
is 6250uV, and different from 8x25 ver.2.0. So, the device is
checked at runtime and the step size is modified if it is 8625q.

Change-Id: Ia4552d24e33eab7072b51d535aa151bcb57e139d
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>