msm: pmic: Add a separate config option for PMIC over RPC

MSMs in which the APPS does not have a direct access to
PMIC (over SSBI) use RPC to communicate with the PMIC.
Create a new config option for this RPC based PMIC driver
and enable it only for the required MSMs (7x27a, 7x30, fsm9xxx).

Change-Id: I668d9840581b8f1f2bdd80da6bdb9445ed560d32
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>