msm: board-8610: add rpm controlled regulator support

Add a call to rpm_regulator_smd_driver_init() in the
msm8610_add_drivers() function so that the rpm regulator
devices are probed in the correct order (before other
devices).

Change-Id: I8b2ef5299c73ff2416315847e2dc389415727eb8
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>