patchpanel: Remove the unused param in ShillClient::ScanDevices()

BUG=None
TEST=unit_tests

Change-Id: Ie03f3d5e72cfcbff68faa70fe5a583f182edd35f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2154293
Tested-by: Jie Jiang <jiejiang@chromium.org>
Commit-Queue: Jie Jiang <jiejiang@chromium.org>
Reviewed-by: Hugo Benichi <hugobenichi@google.com>
Reviewed-by: Garrick Evans <garrick@chromium.org>
diff --git a/patchpanel/arc_service.cc b/patchpanel/arc_service.cc
index 7bc40a6..7d86498 100644
--- a/patchpanel/arc_service.cc
+++ b/patchpanel/arc_service.cc
@@ -207,8 +207,7 @@
   AllocateAddressConfigs();
   shill_client_->RegisterDevicesChangedHandler(
       base::Bind(&ArcService::OnDevicesChanged, weak_factory_.GetWeakPtr()));
-  shill_client_->ScanDevices(
-      base::Bind(&ArcService::OnDevicesChanged, weak_factory_.GetWeakPtr()));
+  shill_client_->ScanDevices();
   shill_client_->RegisterDefaultInterfaceChangedHandler(base::Bind(
       &ArcService::OnDefaultInterfaceChanged, weak_factory_.GetWeakPtr()));
 }