PM / devfreq: export update_devfreq

Allow update_devfreq to be used by devfreq governor built
as modules

Cc: Rajagopal Venkat <[e-mail]>
Cc: MyungJoo Ham <[e-mail]>
Cc: Kyungmin Park <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Kevin Hilman <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

Signed-off-by: Nishanth Menon <[e-mail]>
Acked-by: MyungJoo Ham <[e-mail]>
Signed-off-by: MyungJoo Ham <[e-mail]>

drivers/devfreq/devfreq.c

···
 	devfreq->previous_freq = freq;
 	return err;
 }
+EXPORT_SYMBOL(update_devfreq);
 
 /**
  * devfreq_monitor() - Periodically poll devfreq objects.