tests: Fix ap_wps_er_multi_add_enrollee cleanup steps

Only one of the ERs was stopped at the end of the test case and this
could result in the following test case failing, e.g., when executing
this test case sequence: ap_wps_er_multi_add_enrollee ap_wps_upnp.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

tests/hwsim/test_ap_wps.py

@@ -1195,7 +1195,8 @@ def test_ap_wps_er_multi_add_enrollee(dev, apdev):
     try:
         _test_ap_wps_er_multi_add_enrollee(dev, apdev)
     finally:
-        dev[0].request("WPS_ER_STOP")
+        for i in range(2):
+            dev[i].request("WPS_ER_STOP")
 
 def _test_ap_wps_er_multi_add_enrollee(dev, apdev):
     ssid = "wps-er-add-enrollee"