security: make security_file_set_fowner, f_setown and __f_setown void return

security_file_set_fowner always returns 0, so make it f_setown and
__f_setown void return functions and fix up the error handling in the
callers.

Cc: linux-security-module@vger.kernel.org
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index acaaf67..186ce54 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2152,9 +2152,7 @@
 		goto out;
 
 	if (on) {
-		ret = __f_setown(file, task_pid(current), PIDTYPE_PID, 0);
-		if (ret)
-			goto out;
+		__f_setown(file, task_pid(current), PIDTYPE_PID, 0);
 		tfile->flags |= TUN_FASYNC;
 	} else
 		tfile->flags &= ~TUN_FASYNC;