Linux kernel commit da69a5306ab9 ("selinux: support distinctions among all
network address families") triggers a build error if a new address family
is added without defining a corresponding SELinux security class. As a
result, the smc_socket class was added to the kernel to resolve a build
failure as part of merge commit 3051bf36c25d that introduced AF_SMC circa
Linux 4.11. Define this security class and its access vector, note that it
is enabled as part of the extended_socket_class policy capability, and add
it to the socket_class_set macro.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>