The previous reference counting scheme to enable power resources
got confused when multiple devices were present that might
repeatedly enable or disable the resource and throw off the count.

The new code simply lists the referencing devices which
are requesting the resource to be enabled.  When there are none,
then it is off.
Signed-off-by: Konstantin Karasyov <konstantin.a.karasyov@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>