sock_diag: Arrange sock_diag.h such that it is exportable to userspace

Properly toss existing components around the ifdef __KERNEL__
and include the header into the header-y target.

Signed-off-by: Pavel Emelyanov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/Kbuild

···
 header-y += in.h
 header-y += in6.h
 header-y += in_route.h
+header-y += sock_diag.h
 header-y += inet_diag.h
 header-y += inotify.h
 header-y += input.h

include/linux/sock_diag.h

···
 #ifndef __SOCK_DIAG_H__
 #define __SOCK_DIAG_H__
 
-#define SOCK_DIAG_BY_FAMILY 20
+#include <linux/types.h>
 
-struct sk_buff;
-struct nlmsghdr;
+#define SOCK_DIAG_BY_FAMILY 20
 
 struct sock_diag_req {
 	__u8	sdiag_family;
 	__u8	sdiag_protocol;
 };
+
+#ifdef __KERNEL__
+struct sk_buff;
+struct nlmsghdr;
 
 struct sock_diag_handler {
 	__u8 family;
···
 void sock_diag_save_cookie(void *sk, __u32 *cookie);
 
 extern struct sock *sock_diag_nlsk;
+#endif /* KERNEL */
 #endif