mac80211: Fix power save in change interface

we found that power save is not getting enabled when we do
change interface in this order STA->IBSS->STA. this is
because ieee80211_setup_sdata clears type-dependent union

Reported-by: Leela Kella <leela@qca.qualcomm.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index e895ad5..a984f1f 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2371,6 +2371,7 @@
 		    (unsigned long) sdata);
 
 	ifmgd->flags = 0;
+	ifmgd->powersave = sdata->wdev.ps;
 
 	mutex_init(&ifmgd->mtx);