e1000e: Fix -Wformat-truncation warnings

Provide precision hints to snprintf() since we know the destination
buffer size of the RX/TX ring names are IFNAMSIZ + 5 - 1. This fixes the
following warnings:

drivers/net/ethernet/intel/e1000e/netdev.c: In function
'e1000_request_msix':
drivers/net/ethernet/intel/e1000e/netdev.c:2109:13: warning: 'snprintf'
output may be truncated before the last format character
[-Wformat-truncation=]
     "%s-rx-0", netdev->name);
             ^
drivers/net/ethernet/intel/e1000e/netdev.c:2107:3: note: 'snprintf'
output between 6 and 21 bytes into a destination of size 20
   snprintf(adapter->rx_ring->name,
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     sizeof(adapter->rx_ring->name) - 1,
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     "%s-rx-0", netdev->name);
     ~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/e1000e/netdev.c:2125:13: warning: 'snprintf'
output may be truncated before the last format character
[-Wformat-truncation=]
     "%s-tx-0", netdev->name);
             ^
drivers/net/ethernet/intel/e1000e/netdev.c:2123:3: note: 'snprintf'
output between 6 and 21 bytes into a destination of size 20
   snprintf(adapter->tx_ring->name,
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     sizeof(adapter->tx_ring->name) - 1,
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     "%s-tx-0", netdev->name);
     ~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -2106,7 +2106,7 @@ static int e1000_request_msix(struct e1000_adapter *adapter)
 	if (strlen(netdev->name) < (IFNAMSIZ - 5))
 		snprintf(adapter->rx_ring->name,
 			 sizeof(adapter->rx_ring->name) - 1,
-			 "%s-rx-0", netdev->name);
+			 "%.14s-rx-0", netdev->name);
 	else
 		memcpy(adapter->rx_ring->name, netdev->name, IFNAMSIZ);
 	err = request_irq(adapter->msix_entries[vector].vector,
@@ -2122,7 +2122,7 @@ static int e1000_request_msix(struct e1000_adapter *adapter)
 	if (strlen(netdev->name) < (IFNAMSIZ - 5))
 		snprintf(adapter->tx_ring->name,
 			 sizeof(adapter->tx_ring->name) - 1,
-			 "%s-tx-0", netdev->name);
+			 "%.14s-tx-0", netdev->name);
 	else
 		memcpy(adapter->tx_ring->name, netdev->name, IFNAMSIZ);
 	err = request_irq(adapter->msix_entries[vector].vector,