ath: add common function ath_is_mybeacon

this function is used by most ath driver, so it can be moved here.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/main.c b/drivers/net/wireless/ath/main.c
index 8e99540..8b0ac14 100644
--- a/drivers/net/wireless/ath/main.c
+++ b/drivers/net/wireless/ath/main.c
@@ -59,6 +59,14 @@
 }
 EXPORT_SYMBOL(ath_rxbuf_alloc);
 
+bool ath_is_mybeacon(struct ath_common *common, struct ieee80211_hdr *hdr)
+{
+	return ieee80211_is_beacon(hdr->frame_control) &&
+		!is_zero_ether_addr(common->curbssid) &&
+		ether_addr_equal_64bits(hdr->addr3, common->curbssid);
+}
+EXPORT_SYMBOL(ath_is_mybeacon);
+
 void ath_printk(const char *level, const struct ath_common* common,
 		const char *fmt, ...)
 {