remoteproc: Add support for xo clock

Add xo clock support required to boot up Qualcomm ADSP processor.
The ADSP remoteproc driver keeps xo clock enabled until the
driver receives "handover" irq, in order to allow ADSP processor
to vote for xo clock with rpm.

Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
(cherry picked from commit f33a7358)