cgroups: kernel/ns_cgroup.c should #include <linux/nsproxy.h>

Every file should include the headers containing the externs its global
functions (in this case for ns_cgroup_clone()).

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/ns_cgroup.c

@@ -8,6 +8,7 @@
 #include <linux/cgroup.h>
 #include <linux/fs.h>
 #include <linux/slab.h>
+#include <linux/nsproxy.h>
 
 struct ns_cgroup {
 	struct cgroup_subsys_state css;