[[ https://svnweb.freebsd.org/changeset/base/363079 | r363079 ]] introduced the possibility of loading the SCTP stack as a module in addition to compiling it into the kernel. As part of this, the registration of the system calls was removed and put into the loading of the module. Therefore, the system calls are not registered anymore when compiling the SCTP into the kernel. This patch addresses that.