msm: clock-copper: Add CXO voting support

Replace the stub functions for the cxo clock ops with
a real RPM clock that uses the RPM SMD driver to vote
on CXO when required.

Change-Id: I2ca03cba4f1377ec9b39f998685b3e11f08eea7d
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>