net/mlx5: E-Switch, Replace host_params event with functions_changed event

To support sriov on a E-Switch manager, num_vfs are queried
to the firmware whenever E-Switch manager is notified by
esw_functions_changed event.

Replace host_params event with esw_functions_changed event that reflects
more appropriate naming.

While at it, also correct num_vfs type from int to u16 as expected by
the function mlx5_esw_query_functions().

Signed-off-by: Vu Pham <vuhuong@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>