ixgbe: fix AF_XDP tx packet count

The total_packets count at ixgbe_clean_xdp_tx_irq is
always zero when testing with xdpsock -t -N. Set the gso_segs
to 1 to make the tx packet count correct.

Signed-off-by: William Tu <u9012063@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>