net:CXGB4: fix leak if sk_buff is not used

stable inclusion
from stable-5.10.39
commit 027926f4ff864e0cde03a4e72babb511c7454394
bugzilla: 51881
CVE: NA

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

[ Upstream commit 52bfcdd8 ]

An sk_buff is allocated to send a flow control message, but it's not
sent in all cases: in case the state is not appropiate to send it or if
it can't be enqueued.

In the first of these 2 cases, the sk_buff was discarded but not freed,
producing a memory leak.

Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>