intel_pstate: fix pid_reset to use fixed point values

commit d253d2a526 (Improve accuracy by not truncating until final
result), changed internal variables of the PID to be fixed point
numbers. Update the pid_reset() to reflect this change.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -153,7 +153,7 @@ static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
 	pid->setpoint = setpoint;
 	pid->deadband  = deadband;
 	pid->integral  = int_tofp(integral);
-	pid->last_err  = setpoint - busy;
+	pid->last_err  = int_tofp(setpoint) - int_tofp(busy);
 }
 
 static inline void pid_p_gain_set(struct _pid *pid, int percent)