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>

path: root/timer.h

#ifndef TIMER_H
#define TIMER_H

#include <sys/time.h>

extern void set_itimer_interval_value(struct itimerval *itimer, unsigned long sec,
				      unsigned long usec);

extern int get_user_hz(void);

#endif /* TIMER_H */