PM / devfreq: remove a duplicated kernel-doc markup

The update_devfreq() is also documented at devfreq.c, which
has a more complete note.

So, drop the duplicated markup, in order to avoid this
warning:
	.../Documentation/driver-api/device_link.rst: WARNING: Duplicate C declaration, also defined in 'driver-api/infrastructure'.
	Declaration is 'device_link_state'.

(and to cause a problem with cross-references to it)
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

include/linux/devfreq.h

@@ -228,12 +228,7 @@ int devfreq_resume_device(struct devfreq *devfreq);
 void devfreq_suspend(void);
 void devfreq_resume(void);
 
-/**
- * update_devfreq() - Reevaluate the device and configure frequency
- * @devfreq:	the devfreq device
- *
- * Note: devfreq->lock must be held
- */
+/* update_devfreq() - Reevaluate the device and configure frequency */
 int update_devfreq(struct devfreq *devfreq);
 
 /* Helper functions for devfreq user device driver with OPP. */