batman-adv: Fix includes for IS_ERR/ERR_PTR

IS_ERR/ERR_PTR are not defined in linux/device.h but in linux/err.h. The
files using these macros therefore have to include the correct one.
Reported-by: Linus Luessing <linus.luessing@web.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/debugfs.c

@@ -19,7 +19,7 @@
 #include "main.h"
 
 #include <linux/debugfs.h>
-#include <linux/device.h>
+#include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/export.h>
 #include <linux/fs.h>

net/batman-adv/tp_meter.c

@@ -23,7 +23,7 @@
 #include <linux/byteorder/generic.h>
 #include <linux/cache.h>
 #include <linux/compiler.h>
-#include <linux/device.h>
+#include <linux/err.h>
 #include <linux/etherdevice.h>
 #include <linux/fs.h>
 #include <linux/if_ether.h>