msm: board-samarium: Call rpm-regulator-smd init function

Add a call to rpm_regulator_smd_driver_init() inside of
msmsamarium_add_drivers().  This is used to guarantee that
rpm-regulator-smd devices get probed before all of their
possible consumers.

Change-Id: I0b371595679bf746db42ec5be2241f1d6f81f1fe
Signed-off-by: David Collins <collinsd@codeaurora.org>