net: i40e: shut up uninitialized variable warnings

intel/i40e/i40e_txrx.c: In function 'i40e_xmit_frame_ring':
intel/i40e/i40e_txrx.c:2367:20: error: 'oiph' may be used uninitialized in this function [-Werror=maybe-uninitialized]
intel/i40e/i40e_txrx.c:2317:16: note: 'oiph' was declared here
intel/i40e/i40e_txrx.c:2367:17: error: 'oudph' may be used uninitialized in this function [-Werror=maybe-uninitialized]
intel/i40e/i40e_txrx.c:2316:17: note: 'oudph' was declared here

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -2313,8 +2313,8 @@ static void i40e_tx_enable_csum(struct sk_buff *skb, u32 *tx_flags,
 	struct iphdr *this_ip_hdr;
 	u32 network_hdr_len;
 	u8 l4_hdr = 0;
-	struct udphdr *oudph;
-	struct iphdr *oiph;
+	struct udphdr *oudph = NULL;
+	struct iphdr *oiph = NULL;
 	u32 l4_tunnel = 0;
 
 	if (skb->encapsulation) {