staging:rtl8192u: Replace magic number with defined constant - Style

Replace the magic number '8' with defined constant which is normally used
'MAX_DEV_ADDR_SIZE'.

This is a coding style change which should have no impact on runtime code
execution.
Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c

@@ -217,7 +217,7 @@ inline void softmac_mgmt_xmit(struct sk_buff *skb, struct ieee80211_device *ieee
 	struct rtl_80211_hdr_3addr  *header =
 		(struct rtl_80211_hdr_3addr  *)skb->data;
 
-	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + 8);
+	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 
 	spin_lock_irqsave(&ieee->lock, flags);