usb: class: cdc-wdm: Provide description for usb_cdc_wdm_register()'s manage_power arg

A good attempt was made to document everything else.

Fixes the following W=1 kernel build warning(s):

 drivers/usb/class/cdc-wdm.c:961: warning: Function parameter or member 'manage_power' not described in 'usb_cdc_wdm_register'

Cc: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200715093209.3165641-6-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-wdm.c

@@ -940,7 +940,8 @@ static int wdm_probe(struct usb_interface *intf, const struct usb_device_id *id)
  * @intf: usb interface the subdriver will associate with
  * @ep: interrupt endpoint to monitor for notifications
  * @bufsize: maximum message size to support for read/write
- *
+ * @manage_power: call-back invoked during open and release to
+ *                manage the device's power
  * Create WDM usb class character device and associate it with intf
  * without binding, allowing another driver to manage the interface.
  *