sctp: remove macros sctp_spin_[un]lock_irqrestore

Redefined spin_[un]lock_irqstore to sctp_spin_[un]lock_irqrestore for user
space friendly code which we haven't use in years, so removing them.

Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>