zd1211rw: only update HW beacon if new beacon differs from currect

Update HW beacon only when needed. This appears to make device work in AP-mode
(dtim_period=1) somewhat more stable.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/zd1211rw/zd_mac.h b/drivers/net/wireless/zd1211rw/zd_mac.h
index f8c93c3..c01eca8 100644
--- a/drivers/net/wireless/zd1211rw/zd_mac.h
+++ b/drivers/net/wireless/zd1211rw/zd_mac.h
@@ -165,6 +165,7 @@
 
 struct beacon {
 	struct delayed_work watchdog_work;
+	struct sk_buff *cur_beacon;
 	unsigned long last_update;
 	u16 interval;
 	u8 period;