ath9k_htc: Remove useless cancel_work_sync

There is no need to cancel the PS work when disassociation
happens. The work handlers are cancelled in the stop()
callback.
Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/htc_drv_main.c

@@ -1632,7 +1632,6 @@ static void ath9k_htc_bss_info_changed(struct ieee80211_hw *hw,
 			ath_start_ani(priv);
 		} else {
 			priv->op_flags &= ~OP_ASSOCIATED;
-			cancel_work_sync(&priv->ps_work);
 			cancel_delayed_work_sync(&priv->ath9k_ani_work);
 		}
 	}