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>