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 <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index 0b091b3..8e484d6 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -195,6 +195,7 @@
 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