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

Add a call to rpm_regulator_smd_driver_init() inside of
msm_copper_add_drivers().  This is used to guarantee that
drivers get probed in the correct order based upon inter-driver
dependencies.

Change-Id: I766109c9e71ba83a5637f87360886b005f96e1ae
Signed-off-by: David Collins <collinsd@codeaurora.org>