net/mlx5e: Fix wrong xmit_more application

Cited patch refactored the xmit_more indication while not preserving
its functionality. Fix it.

Fixes: 3c31ff22 ("drivers: mellanox: use netdev_xmit_more() helper")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>