greybus: es2: demote dynamic-urb error message

Demote error message when needing to dynamically allocate an URB to
debug level.

This isn't really an error as much as a reminder of how the current es2
implementation works: It uses a fixed number of pre-allocated URBs, but
allocates URBs dynamically when enough messages are sent in rapid
succession to exhaust the URB pool.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/es2.c

@@ -274,7 +274,7 @@ static struct urb *next_free_urb(struct es2_ap_dev *es2, gfp_t gfp_mask)
 	 * Crap, pool is empty, complain to the syslog and go allocate one
 	 * dynamically as we have to succeed.
 	 */
-	dev_err(&es2->usb_dev->dev,
+	dev_dbg(&es2->usb_dev->dev,
 		"No free CPort OUT urbs, having to dynamically allocate one!\n");
 	return usb_alloc_urb(0, gfp_mask);
 }