net/eth: Clean up local variable shadowing

net/eth: Clean up local variable shadowing

Fix:

  net/eth.c:435:20: error: declaration shadows a local variable [-Werror,-Wshadow]
            size_t input_size = iov_size(pkt, pkt_frags);
                   ^
  net/eth.c:413:16: note: previous declaration is here
        size_t input_size = iov_size(pkt, pkt_frags);
               ^

Suggested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230904161235.84651-16-philmd@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>