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>