thermal: intel: powerclamp: Return last requested state as cur_state

When the user is reading cur_state from the thermal cooling device for
Intel powerclamp device:
 - It returns the idle ratio from Package C-state counters when
   there is active idle injection session.
 - -1, when there is no active idle injection session.

This information is not very useful as the package C-state counters vary
a lot from read to read. Instead just return the last requested cur_state.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>