ixgbe: cleanup variable initialization

The ixgbe_fcoe_ddp_get function wasn't initializing one of its variables
and this was producing compiler warnings.  This patch cleans that up.
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ixgbe/ixgbe_fcoe.c

@@ -165,7 +165,7 @@ int ixgbe_fcoe_ddp_get(struct net_device *netdev, u16 xid,
 	unsigned int thisoff = 0;
 	unsigned int thislen = 0;
 	u32 fcbuff, fcdmarw, fcfltrw;
-	dma_addr_t addr;
+	dma_addr_t addr = 0;
 
 	if (!netdev || !sgl)
 		return 0;