[SCTP]: Don't export include/linux/sctp.h to userspace.

This file contains protocol definitions and there are no SCTP apps
that use this file.
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/Kbuild

@@ -137,7 +137,6 @@ header-y += radeonfb.h
 header-y += raw.h
 header-y += resource.h
 header-y += rose.h
-header-y += sctp.h
 header-y += smbno.h
 header-y += snmp.h
 header-y += sockios.h