wimax: i2400: fix memory leak

mainline inclusion
from mainline-v5.3
commit 2507e6ab7a9a440773be476141a255934468c5ef
category: bugfix
bugzilla: 13690
CVE: CVE-2019-19051

-------------------------------------------------

In i2400m_op_rfkill_sw_toggle cmd buffer should be released along with
skb response.
Signed-off-by: NNavid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NWenan Mao <maowenan@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/wimax/i2400m/op-rfkill.c

@@ -142,6 +142,7 @@ int i2400m_op_rfkill_sw_toggle(struct wimax_dev *wimax_dev,
 			"%d\n", result);
 	result = 0;
 error_cmd:
+	kfree(cmd);
 	kfree_skb(ack_skb);
 error_msg_to_dev:
 error_alloc: