mlxsw: Move a mirroring check to mlxsw_sp_span_entry_create

The check for whether a mirror port (which is a mlxsw front panel port)
belongs to the same mlxsw instance as the mirrored port, is currently
only done in spectrum_acl, even though it's applicable for the matchall
case as well. Thus move it to mlxsw_sp_span_entry_create().

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>