wireless: Use eth_<foo>_addr instead of memset

Use the built-in function instead of memset.

Miscellanea:

Add #include <linux/etherdevice.h> where appropriate
Use ETH_ALEN instead of 6

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wireless/iwlegacy/common.c b/drivers/net/wireless/iwlegacy/common.c
index 2c4fa49..8871145 100644
--- a/drivers/net/wireless/iwlegacy/common.c
+++ b/drivers/net/wireless/iwlegacy/common.c
@@ -4634,7 +4634,7 @@
 	il->vif = NULL;
 	il->iw_mode = NL80211_IFTYPE_UNSPECIFIED;
 	il_teardown_interface(il, vif);
-	memset(il->bssid, 0, ETH_ALEN);
+	eth_zero_addr(il->bssid);
 
 	D_MAC80211("leave\n");
 	mutex_unlock(&il->mutex);