RDMA/cxgb4: Check skb value for failure to allocate

get_skb() can fail to allocate skb, so check it.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 5be78ee9 ("RDMA/cxgb4: Fix LE hash collision bug for active open connection")
Signed-off-by: Artem Chernyshev <artem.chernyshev@red-soft.ru>
Link: https://lore.kernel.org/r/20230905124048.284165-1-artem.chernyshev@red-soft.ru


Signed-off-by: Leon Romanovsky <leon@kernel.org>