vts: Fix incorrect instance name in Teardown

The stopHostapd uses vendor HAL HIDL interface.
The interface name should use wifi_instance.

Bug: 161682236
Test: atest VtsHalWifiHostapdV1_2TargetTest
Change-Id: I8215cba3e2a36f48863f57e199684c7446e20692
Merged-In: I8215cba3e2a36f48863f57e199684c7446e20692
diff --git a/wifi/hostapd/1.2/vts/functional/hostapd_hidl_test.cpp b/wifi/hostapd/1.2/vts/functional/hostapd_hidl_test.cpp
index 2715891..a39f064 100644
--- a/wifi/hostapd/1.2/vts/functional/hostapd_hidl_test.cpp
+++ b/wifi/hostapd/1.2/vts/functional/hostapd_hidl_test.cpp
@@ -72,7 +72,7 @@
             "wifi_softap_wpa3_sae_supported");
     }
 
-    virtual void TearDown() override { stopHostapd(hostapd_instance_name_); }
+    virtual void TearDown() override { stopHostapd(wifi_instance_name_); }
 
    protected:
     bool isWpa3SaeSupport_ = false;