configfs: Minimize #include directives

Only include the header files that are needed by configfs.h itself.
Add #include <linux/stat.h>.
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>

include/linux/configfs.h

@@ -35,14 +35,11 @@
 #ifndef _CONFIGFS_H_
 #define _CONFIGFS_H_
 
-#include <linux/kernel.h>
-#include <linux/types.h>
-#include <linux/list.h>
-#include <linux/kref.h>
-#include <linux/mutex.h>
-#include <linux/err.h>
-
-#include <linux/atomic.h>
+#include <linux/stat.h>   /* S_IRUGO */
+#include <linux/types.h>  /* ssize_t */
+#include <linux/list.h>   /* struct list_head */
+#include <linux/kref.h>   /* struct kref */
+#include <linux/mutex.h>  /* struct mutex */
 
 #define CONFIGFS_ITEM_NAME_LEN	20