PM / devfreq: event: remove duplicate devfreq_event_get_drvdata()

there define two devfreq_event_get_drvdata() function in devfreq-event.h
when disable CONFIG_PM_DEVFREQ_EVENT, it will lead to build fail. So
remove devfreq_event_get_drvdata() function.

Fixes: f262f28c1470 ("PM / devfreq: event: Add devfreq_event class")
Cc: [e-mail]
Signed-off-by: Lin Huang <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>
Signed-off-by: MyungJoo Ham <[e-mail]>

include/linux/devfreq-event.h

···
 	return -EINVAL;
 }
 
-static inline void *devfreq_event_get_drvdata(struct devfreq_event_dev *edev)
-{
-	return ERR_PTR(-EINVAL);
-}
-
 static inline struct devfreq_event_dev *devfreq_event_get_edev_by_phandle(
 					struct device *dev, int index)
 {