net: dsa: lantiq_gswip: Improve error message in gswip_port_fdb()

Print that no FID is found for bridge %s instead of the incorrect
message that the port is not part of a bridge.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Link: https://lore.kernel.org/r/20240611135434.3180973-13-ms@dev.tdt.de


Signed-off-by: Jakub Kicinski <kuba@kernel.org>