tcp: tcp_set_window_clamp() cleanup

Remove one indentation level.

Use max_t() and clamp() macros.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250301201424.2046477-7-edumazet@google.com


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