spin_is_locked() on a non !SMP build is kind of useless.

BUG_ON(!spin_is_locked(xx)) is guaranteed to crash.

Just remove this check in reqsk_fastopen_remove() as
the callers do hold the socket lock.
Reported-by: NKetan Kulkarni <ketkulka@gmail.com>
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Jerry Chu <hkchu@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Dave Taht <dave.taht@gmail.com>
Acked-by: NH.K. Jerry Chu <hkchu@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>