devfreq_cooling: pass a pointer to devfreq in the power model callbacks

When the devfreq cooling device was designed, it was an oversight not to
pass a pointer to the struct devfreq as the first parameters of the
callbacks.  The design patterns of the kernel suggest it for a good
reason.

By passing a pointer to struct devfreq, the driver can register one
function that works with multiple devices.  With the current
implementation, a driver that can work with multiple devices has to
create multiple copies of the same function with different parameters so
that each devfreq_cooling_device can use the appropriate one.  By
passing a pointer to struct devfreq, the driver can identify which
device it's referring to.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Reviewed-by: Punit Agrawal <punit.agrawal@arm.com>
Reviewed-by: Ørjan Eide <orjan.eide@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

include/linux/devfreq_cooling.h

@@ -36,8 +36,10 @@
  *			@dyn_power_coeff * frequency * voltage^2
  */
 struct devfreq_cooling_power {
-	unsigned long (*get_static_power)(unsigned long voltage);
-	unsigned long (*get_dynamic_power)(unsigned long freq,
+	unsigned long (*get_static_power)(struct devfreq *devfreq,
+					  unsigned long voltage);
+	unsigned long (*get_dynamic_power)(struct devfreq *devfreq,
+					   unsigned long freq,
 					   unsigned long voltage);
 	unsigned long dyn_power_coeff;
 };