ixgbe: Fix cls_u32 offload support for fields with masks

Remove the incorrect check for mask in ixgbe_configure_clsu32 and
drop the 'mask' field that is not required in struct ixgbe_mat_field

Verified with the following filters:

 #tc qdisc add dev p4p1 ingress
 #tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
	handle 800:0:1 u32 ht 800: \
	match ip dst 10.0.0.1/8 match ip src 10.0.0.2/8 action drop
 #tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
	handle 800:0:2 u32 ht 800: \
	match ip dst 11.0.0.1/16 match ip src 11.0.0.2/16 action drop
 #tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
	handle 800:0:3 u32 ht 800: \
	match ip dst 12.0.0.1/24 match ip src 12.0.0.2/24 action drop
 #tc filter add dev p4p1 parent ffff: protocol ip prio 99 \
	handle 800:0:4 u32 ht 800: \
	match ip dst 13.0.0.1/32 match ip src 13.0.0.2/32 action drop

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>