ionic: account for vlan tag len in rx buffer len

Let the FW know we have enough receive buffer space for the
vlan tag if it isn't stripped.

Fixes: 0f3154e6 ("ionic: Add Tx and Rx handling")
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Link: https://lore.kernel.org/r/20201218215001.64696-1-snelson@pensando.ioSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/pensando/ionic/ionic_txrx.c

@@ -337,7 +337,7 @@ void ionic_rx_fill(struct ionic_queue *q)
 	unsigned int i, j;
 	unsigned int len;
 
-	len = netdev->mtu + ETH_HLEN;
+	len = netdev->mtu + ETH_HLEN + VLAN_HLEN;
 	nfrags = round_up(len, PAGE_SIZE) / PAGE_SIZE;
 
 	for (i = ionic_q_space_avail(q); i; i--) {