net: ethernet: lantiq_etop: remove unused variable

Remove a variable that has never been used.

Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Link: https://patch.msgid.link/20240815074956.155224-1-olek2@wp.pl


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