net/hns3: fix VF mailbox message handling

VF's command receive queue was mainly used to receive mailbox messages
from PF. There are two type mailbox messages: request response message
and message pushed by PF.

There are two types of threads that can handle these messages:
1) the interrupt thread of the main process: it could handle both types
of messages.
2) other threads: it could only handle request response messages.

The collaboration mechanism between the two type threads is that other
threads set the opcode of processed messages to zero so that the
interrupt thread of the main process does not process these messages
again.

Unfortunately, the other threads mark the message pointed to by the
crq->next-to-use variable which is fixed in the loop, not the message
pointed to by the next-to-use variable.

Fixes: dbbbad23e3 ("net/hns3: fix VF handling LSC event in secondary process")
Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>

drivers/net/hns3/hns3_mbx.c

@@ -429,7 +429,7 @@ hns3_handle_mbx_msg_out_intr(struct hns3_hw *hw)
 			 * Clear opcode to inform intr thread don't process
 			 * again.
 			 */
-			crq->desc[crq->next_to_use].opcode = 0;
+			crq->desc[next_to_use].opcode = 0;
 		}
 
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