net/mlx5: E-Switch, Fix vport enable flow

Reorder vport enable flow to mark the vport as enabled before calling
the vport change handler which was modified to handle the case for
when vport is not enabled.

This fixes the case for when the PF netdev is open before sriov is
enabled, once sriov is enabled at esw_enable_vport,
esw_vport_change_handle_locked didn't read the PF context since it
thought the PF vport was not enabled.

When we enable the vport, arming for events is not required anymore,
since it's done on the vport change handle

Fixes: 586cfa7f ('net/mlx5: E-Switch, Use vport event handler for vport cleanup')
Signed-off-by: Mohamad Haj Yahia <mohamad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>