batman-adv: Drop compat-hack for __poll_t

__poll_t is already defined by the mac80211's backports and
doesn't have to be redefined in the compat-hacks.h.

Signed-off-by: Sven Eckelmann <sven@narfation.org>

batman-adv/src/compat-hacks.h

@@ -167,13 +167,6 @@ static inline int batadv_cfg80211_get_station(struct net_device *dev,
 
 #endif /* < KERNEL_VERSION(4, 18, 0) */
 
-
-#ifdef __CHECK_POLL
-typedef unsigned __bitwise __poll_t;
-#else
-typedef unsigned __poll_t;
-#endif
-
 #endif /* < KERNEL_VERSION(4, 16, 0) */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(5, 0, 0)