ath9k: restore power state on set channel failure

Not doing so, could cause imbalance in powersave count.

Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index c0f478b..e655f2a 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1258,6 +1258,7 @@
 		if (ath_set_channel(sc, hw, &sc->sc_ah->channels[pos]) < 0) {
 			ath_err(common, "Unable to set channel\n");
 			mutex_unlock(&sc->mutex);
+			ath9k_ps_restore(sc);
 			return -EINVAL;
 		}