mlxsw: spectrum_span: Rename misnamed variable l3edev

Calling the variable l3edev was relevant when neighbor lookup was the
last stage in the simulated pipeline. Now that mlxsw handles bridges and
vlan devices as well, calling it "L3" is a misnomer.

Thus in mlxsw_sp_span_dmac(), rename to "dev", because that function is
just a service routine where the distinction between tunnel and egress
device isn't necessary.

In mlxsw_sp_span_entry_tunnel_parms_common(), rename to "edev" to
emphasize that the routine traces packet egress.

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>