msm: 9615: Support for corner volages during sleep.

On 9615, the regulators send a voltage level instead of a actual voltage
value for digital voltage rail. Change rpm resources platform data to
account for level based voting.

Change-Id: I6d412d6f60ac47012a442cdb90704159cf298d95
CRs-fixed: 354458
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
Signed-off-by: David Collins <collinsd@codeaurora.org>