The Rx listener abstraction allows the switch driver (e.g.,
mlxsw_spectrum) to register a function that is called when a packet is
received (trapped) for a specific reason.

Up until now, the Rx listener lookup was solely based on the trap
identifier. However, when a packet is mirrored to the CPU the trap
identifier merely indicates that the packet was mirrored, but not why it
was mirrored. This makes it impossible for the switch driver to register
different Rx listeners for different mirror reasons.

Solve this by allowing the switch driver to register a Rx listener with
a mirror reason and by extending the Rx listener lookup to take the
mirror reason into account.
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>