Include kernel.h from configfs.h

configfs.h uses the container_of macro and as such should include kernel.h.
Signed-off-by: Ben Nizette <bn@niasdigital.com>
Cc: Joel Becker <Joel.Becker@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/configfs.h

@@ -37,6 +37,7 @@
 
 #ifdef __KERNEL__
 
+#include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/kref.h>