mlxsw: spectrum_span: Add driver private info to parms_set() callback

The parms_set() callback is supposed to fill in the parameters for the
SPAN agent, such as the destination port and encapsulation info, if any.

When mirroring to the CPU port we cannot resolve the destination port
(the CPU port) without access to the driver private info.

Pass the driver private info to parms_set() callback so that it could be
used later on to resolve the CPU port.

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>