vlan: vlan_changelink() should propagate errors

Both vlan_dev_change_flags() and vlan_dev_set_egress_priority()
can return an error. vlan_changelink() should not ignore them.

Fixes: 07b5b17e ("[VLAN]: Use rtnl_link API")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>