staging: isdn: remove unnecessary parentheses

Fix the following checkpatch error:

ERROR: return is not a function, parentheses are not required
FILE: drivers/staging/isdn/hysdn/hysdn_net.c:289:
+        return (0);                /* and return success */
Signed-off-by: Thiago Bonotto <thbonotto@gmail.com>
Link: https://lore.kernel.org/r/20190802202323.27117-1-thbonotto@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/isdn/hysdn/hysdn_net.c

@@ -286,7 +286,7 @@ hysdn_net_create(hysdn_card *card)
 
 	if (card->debug_flags & LOG_NET_INIT)
 		hysdn_addlog(card, "network device created");
-	return (0);		/* and return success */
+	return 0;		/* and return success */
 }				/* hysdn_net_create */
 
 /***************************************************************************/