staging: brcm80211: remove setting ssn to zero upon AMPDU_TX_START

The ssn should be given a valid value by the driver or it should not
override the value. Removed override to zero from the driver.
Reported-by: NJohannes Berg <johannes@sipsolutions.net>
Reviewed-by: NPieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: NRoland Vossen <rvossen@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/brcm80211/brcmsmac/mac80211_if.c

@@ -669,11 +669,6 @@ brcms_ops_ampdu_action(struct ieee80211_hw *hw,
 				  tid);
 			return -EINVAL;
 		}
-		/*
-		 * Future improvement:
-		 *   Use the starting sequence number provided ...
-		 */
-		*ssn = 0;
 		ieee80211_start_tx_ba_cb_irqsafe(vif, sta->addr, tid);
 		break;