staging: comedi: return void from comedi_driver_unregister()

'Unregister' functions generally return `void`.
`comedi_driver_unregister()` currently returns an `int` errno value.
Nothing looks at the return value.  Change the return type to `void`.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -363,7 +363,7 @@ int comedi_auto_config(struct device *, struct comedi_driver *,
 void comedi_auto_unconfig(struct device *);
 
 int comedi_driver_register(struct comedi_driver *);
-int comedi_driver_unregister(struct comedi_driver *);
+void comedi_driver_unregister(struct comedi_driver *);
 
 /**
  * module_comedi_driver() - Helper macro for registering a comedi driver

drivers/staging/comedi/drivers.c

@@ -559,7 +559,7 @@ int comedi_driver_register(struct comedi_driver *driver)
 }
 EXPORT_SYMBOL_GPL(comedi_driver_register);
 
-int comedi_driver_unregister(struct comedi_driver *driver)
+void comedi_driver_unregister(struct comedi_driver *driver)
 {
 	struct comedi_driver *prev;
 	int i;
@@ -584,15 +584,14 @@ int comedi_driver_unregister(struct comedi_driver *driver)
 
 	if (comedi_drivers == driver) {
 		comedi_drivers = driver->next;
-		return 0;
+		return;
 	}
 
 	for (prev = comedi_drivers; prev->next; prev = prev->next) {
 		if (prev->next == driver) {
 			prev->next = driver->next;
-			return 0;
+			return;
 		}
 	}
-	return -EINVAL;
 }
 EXPORT_SYMBOL_GPL(comedi_driver_unregister);