PM / devfreq: msmcci-hwmon: Add provision for normal reg access

On some systems, scm calls for cci registers are not supported.
Use normal writel/readl in those cases. Add device tree flag to
distinguish them.

Change-Id: Icfb609d43f888856786c1881b2ee34ffd501e37a
Signed-off-by: Arun KS <arunks@codeaurora.org>