mlxsw: spectrum_switchdev: Remove unused variables

After 1ecb1957 ("mlxsw: spectrum_switchdev: Remove getting
PORT_BRIDGE_FLAGS") we are not accessing any driver private data
structure, so the mlxsw_sp_port and mlxsw_sp variables are unused.

Fixes: 1ecb1957

 ("mlxsw: spectrum_switchdev: Remove getting PORT_BRIDGE_FLAGS")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>