net: dsa: qca8k: do not write port mask twice in bridge join/leave

qca8k_port_bridge_join() set QCA8K_PORT_LOOKUP_CTRL() for i == port twice,
once in the loop handling all other port's masks, and finally at the end
with the accumulated port_mask.

The first time it would incorrectly set the port's own bit in the mask,
only to correct the mistake a moment later. qca8k_port_bridge_leave() had
the same issue, but here the regmap_clear_bits() was a no-op rather than
setting an unintended value.

Remove the duplicate assignment by skipping the whole loop iteration for
i == port. The unintended bit setting doesn't seem to have any negative
effects (even when not reverted right away), so the change is submitted
as a simple cleanup rather than a fix.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>