mlxsw: spectrum_trap: Move functions to avoid their forward declarations

No need to have forward declarations for mlxsw_sp_rx_drop_listener()
and mlxsw_sp_rx_exception_listener(). Just move them up and avoid it.

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