selinux: use kernel linux/socket.h for genheaders and mdp

When compiling genheaders and mdp from a newer host kernel, the
following error happens:

    In file included from scripts/selinux/genheaders/genheaders.c:18:
    ./security/selinux/include/classmap.h:238:2: error: #error New
    address family defined, please update secclass_map.  #error New
    address family defined, please update secclass_map.  ^~~~~
    make[3]: *** [scripts/Makefile.host:107:
    scripts/selinux/genheaders/genheaders] Error 1 make[2]: ***
    [scripts/Makefile.build:599: scripts/selinux/genheaders] Error 2
    make[1]: *** [scripts/Makefile.build:599: scripts/selinux] Error 2
    make[1]: *** Waiting for unfinished jobs....

Instead of relying on the host definition, include linux/socket.h in
classmap.h to have PF_MAX.

Signed-off-by: Paulo Alcantara <paulo@paulo.ac>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
[PM: manually merge in mdp.c, subject line tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>

scripts/selinux/genheaders/genheaders.c

@@ -9,7 +9,6 @@
 #include <string.h>
 #include <errno.h>
 #include <ctype.h>
-#include <sys/socket.h>
 
 struct security_class_mapping {
 	const char *name;

scripts/selinux/mdp/mdp.c

@@ -32,7 +32,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
-#include <sys/socket.h>
 #include <linux/kconfig.h>
 
 static void usage(char *name)

security/selinux/include/classmap.h

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <linux/capability.h>
+#include <linux/socket.h>
 
 #define COMMON_FILE_SOCK_PERMS "ioctl", "read", "write", "create", \
     "getattr", "setattr", "lock", "relabelfrom", "relabelto", "append", "map"