net/vmxnet3: fix build with clang 13

The completed variable is used for debug logs even though clang 13
reports it as unused.

Bugzilla ID: 881
Fixes: c3ecdbb ("vmxnet3: support TSO")
Cc: stable@dpdk.org

Reported-by: Liang Longfeng <longfengx.liang@intel.com>
Signed-off-by: Conor Walsh <conor.walsh@intel.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>

drivers/net/vmxnet3/vmxnet3_rxtx.c

@@ -340,6 +340,9 @@ vmxnet3_tq_tx_complete(vmxnet3_tx_queue_t *txq)
 	}
 
 	PMD_TX_LOG(DEBUG, "Processed %d tx comps & command descs.", completed);
+
+	/* To avoid compiler warnings when not in DEBUG mode. */
+	RTE_SET_USED(completed);
 }
 
 uint16_t