PM / devfreq: msmcci-hwmon: Add support for handling shared irq

Some targets have a single irq line which is shared among all
the cci hwmon counters. Enhance the driver to support shared interrupt
handling.

Change-Id: I5fdaecfaa14fa47e8f393fe51c538e5000e6ad5b
Signed-off-by: Arun KS <arunks@codeaurora.org>
Signed-off-by: Hanumath Prasad <hpprasad@codeaurora.org>