net: sctp: Fix some typos

Modify "unkown" to "unknown" in net/sctp/sm_make_chunk.c and
Modify "orginal" to "original" in net/sctp/socket.c.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Lu Wei <luwei32@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>