cpufreq: qcom: cpufreq-hw: Add support for SDPM rail voting

Add support for shared digital rail vote for MX/CX when there is a
transition in the frequency of the CPU. Also add the suspend/resume
callbacks where the driver will vote for the minimum CPU frequency
during suspend and restore back once back in resume.

Change-Id: I26a5f65b0001551bd09c28902810c72fa9c9719a
Signed-off-by: Taniya Das <tdas@codeaurora.org>