net: gso_test: release each segment individually

consume_skb() doesn't walk the segment list, so segments other than
the first are leaked.

Move this skb_consume call into the loop.

Cc: Willem de Bruijn <willemb@google.com>
Fixes: b3098d32 ("net: add skb_segment kunit test")
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>