thermal: intel_powerclamp: Remove accounting for IRQ wakes

There is a static variable "idle_wakeup_counter", which accounts for
number of wake ups because of IRQs and take actions to compensate idle
injection. This is now read and reset to 0, but never incremented.
So all the usage of this counter for idle injection has no use.

Also another static variable "reduce_irq", which depends on
"idle_wakeup_counter", so remove usage of "reduce_irq" also.

Commit feb6cd6a ("thermal/intel_powerclamp: stop sched tick in
forced idle") replaced the local use of "mwait_idle_with_hints" with
play_idle(). This removed possibility of updating "idle_wakeup_counter"
without change in play_idle(). This change was made in Linux 4.10.

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