Set extended advertising parameters upon first use of API v2

Previously, extended advertising parameters failed to be set
during BLE initialisation when the stack was not ready.

To work around this, we delay it to the first use of
useVersionTwoAPI.

Author: LDong-Arm

features/FEATURE_BLE/source/generic/GenericGap.tpp

@@ -457,17 +457,6 @@ GenericGap<PalGapImpl, PalSecurityManager, ConnectionEventMonitorEventHandler>::
     _random_static_identity_address = _pal_gap.get_random_address();
 
     _pal_gap.set_event_handler(this);
-
-#if BLE_FEATURE_EXTENDED_ADVERTISING
-    if (is_extended_advertising_available()) {
-        setExtendedAdvertisingParameters(
-            LEGACY_ADVERTISING_HANDLE,
-            AdvertisingParameters()
-        );
-    }
-
-    _existing_sets.set(LEGACY_ADVERTISING_HANDLE);
-#endif // BLE_FEATURE_EXTENDED_ADVERTISING
 }
 
 template <template<class> class PalGapImpl, class PalSecurityManager, class ConnectionEventMonitorEventHandler>
@@ -3470,7 +3459,19 @@ void GenericGap<PalGapImpl, PalSecurityManager, ConnectionEventMonitorEventHandl
     if (_deprecated_scan_api_used) {
         MBED_ERROR(mixed_scan_api_error, "Use of up to date scan API with deprecated API");
     }
-    _non_deprecated_scan_api_used = true;
+    if (!_non_deprecated_scan_api_used) {
+        _non_deprecated_scan_api_used = true;
+#if BLE_FEATURE_EXTENDED_ADVERTISING
+        if (const_cast<GenericGap*>(this)->is_extended_advertising_available()) {
+            const_cast<GenericGap*>(this)->setExtendedAdvertisingParameters(
+                LEGACY_ADVERTISING_HANDLE,
+                AdvertisingParameters()
+            );
+        }
+        const_cast<BitArray<MAX_ADVERTISING_SETS>*>(&_existing_sets)->set(LEGACY_ADVERTISING_HANDLE);
+#endif
+    }
+
 }
 
 template <template<class> class PalGapImpl, class PalSecurityManager, class ConnectionEventMonitorEventHandler>