tcp: Clean up reverse xmas tree in cookie_v[46]_check().

We will grow and cut the xmas tree in cookie_v[46]_check().
This patch cleans it up to make later patches tidy.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231129022924.96156-2-kuniyu@amazon.com


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