unix_diag: Include unix_diag.h into header-y target

The headers check complains it should include the linux/types.h
withing, thus add this one.

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 8e484d6..c94e717 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -197,6 +197,7 @@
 header-y += in_route.h
 header-y += sock_diag.h
 header-y += inet_diag.h
+header-y += unix_diag.h
 header-y += inotify.h
 header-y += input.h
 header-y += ioctl.h