i40e: fix flow director packet filter programming

Initialize to zero structures to build a valid
Tx Packet used for the filter programming.

Fixes: a9219b33 ("i40e: VLAN field for flow director")
Signed-off-by: Radoslaw Tyl <radoslawx.tyl@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Arpana Arland <arpanax.arland@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>