rds: remove the unneed NULL checking

unregister_net_sysctl_table will check the ctl_table_header,
so remove the unneed checking

Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/iw_sysctl.c b/net/rds/iw_sysctl.c
index 89c9151..139239d 100644
--- a/net/rds/iw_sysctl.c
+++ b/net/rds/iw_sysctl.c
@@ -111,8 +111,7 @@
 
 void rds_iw_sysctl_exit(void)
 {
-	if (rds_iw_sysctl_hdr)
-		unregister_net_sysctl_table(rds_iw_sysctl_hdr);
+	unregister_net_sysctl_table(rds_iw_sysctl_hdr);
 }
 
 int rds_iw_sysctl_init(void)