net: aquantia: fix out of memory condition on rx side

[ Upstream commit be6cef69ba570ebb327eba1ef6438f7af49aaf86 ]

On embedded environments with hard memory limits it is a normal although
rare case when skb can't be allocated on rx part under high traffic.

In such OOM cases napi_complete_done() was not called.
So the napi object became in an invalid state like it is "scheduled".
Kernel do not re-schedules the poll of that napi object.

Consequently, kernel can not remove that object the system hangs on
`ifconfig down` waiting for a poll.

We are fixing this by gracefully closing napi poll routine with correct
invocation of napi_complete_done.

This was reproduced with artificially failing the allocation of skb to
simulate an "out of memory" error case and check that traffic does
not get stuck.

Fixes: 970a2e98 ("net: ethernet: aquantia: Vector operations")
Signed-off-by: NIgor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: NDmitry Bogdanov <dmitry.bogdanov@aquantia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>

drivers/net/ethernet/aquantia/atlantic/aq_vec.c

@@ -89,6 +89,7 @@ static int aq_vec_poll(struct napi_struct *napi, int budget)
 			}
 		}
 
+err_exit:
 		if (!was_tx_cleaned)
 			work_done = budget;
 
@@ -98,7 +99,7 @@ static int aq_vec_poll(struct napi_struct *napi, int budget)
 					1U << self->aq_ring_param.vec_idx);
 		}
 	}
-err_exit:
+
 	return work_done;
 }