From: Sven Eckelmann <sven@narfation.org>
Date: Mon, 14 Sep 2020 13:58:16 +0200
Subject: batman-adv: Add missing include for in_interrupt()

The fix for receiving (internally generated) bla packets outside the
interrupt context introduced the usage of in_interrupt(). But this
functionality is only defined in linux/preempt.h which was not included
with the same patch.

Fixes: 3747f81a1380 ("batman-adv: bla: use netif_rx_ni when not in interrupt context")
Signed-off-by: Sven Eckelmann <sven@narfation.org>

Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/6ea99cd9c82b2d1bc4a313fe9006bcf5d956380e

--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -25,6 +25,7 @@
 #include <linux/lockdep.h>
 #include <linux/netdevice.h>
 #include <linux/netlink.h>
+#include <linux/preempt.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
 #include <linux/seq_file.h>