sctp: remove the unnecessary state check in sctp_outq_tail

Data Chunks are only sent by sctp_primitive_SEND, in which sctp checks
the asoc's state through statetable before calling sctp_outq_tail. So
there's no need to check the asoc's state again in sctp_outq_tail.

Besides, sctp_do_sm is protected by lock_sock, even if sending msg is
interrupted by timer events, the event's processes still need to acquire
lock_sock first. It means no others CMDs can be enqueue into side effect
list before CMD_SEND_MSG to change asoc->state, so it's safe to remove it.

This patch is to remove redundant asoc->state check from sctp_outq_tail.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>