hostapd(vts): Use the correct syntax for vendor prop

Change the prop to add "ro.vendor." prefix for the new vendor prop.

Bug: 136645414
Change-Id: I5edfdc98991068eac279975397b6a29313bf31da
diff --git a/wifi/hostapd/1.1/vts/functional/hostapd_hidl_test.cpp b/wifi/hostapd/1.1/vts/functional/hostapd_hidl_test.cpp
index 7aaad02..ffd4d97 100644
--- a/wifi/hostapd/1.1/vts/functional/hostapd_hidl_test.cpp
+++ b/wifi/hostapd/1.1/vts/functional/hostapd_hidl_test.cpp
@@ -56,7 +56,8 @@
    protected:
     std::string getPrimaryWlanIfaceName() {
         std::array<char, PROPERTY_VALUE_MAX> buffer;
-        auto res = property_get("wifi.sap.interface", buffer.data(), nullptr);
+        auto res = property_get("ro.vendor.wifi.sap.interface",
+                                buffer.data(), nullptr);
         if (res > 0) return buffer.data();
         property_get("wifi.interface", buffer.data(), "wlan0");
         return buffer.data();