net: txgbe: initialize num_q_vectors for MSI/INTx interrupts

When using MSI/INTx interrupts, wx->num_q_vectors is uninitialized.
Thus there will be kernel panic in wx_alloc_q_vectors() to allocate
queue vectors.

Fixes: 3f70318 ("net: libwx: Add irq flow functions")
Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Jiawen Wu

drivers/net/ethernet/wangxun/libwx/wx_lib.c

@@ -1686,6 +1686,7 @@ static int wx_set_interrupt_capability(struct wx *wx)
 	}
 
 	pdev->irq = pci_irq_vector(pdev, 0);
+	wx->num_q_vectors = 1;
 
 	return 0;
 }