mlxsw: core: Allow to register disabled traps using MLXSW_RXL_DIS

Introduce a new macro MLXSW_RXL_DIS that allows to register listeners
as disabled. That allows that from now on, the "action" can be
understood always as "enabled action" and "unreg_action" as "disabled
action". Rename them and treat them accordingly.

Use the new macro for defining drops in spectrum_trap.c.

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>