[ECM] Only restrict settings on handheld

ECM was designed to work on all form factors, but for now, we're
focusing only on handheld.

Fix: 324436878
Test: Test: atest CtsPermissionUiTestCases:android.permissionui.cts.EnhancedConfirmationManagerTest
Change-Id: I662a810ac47ebd6e20e8a9cdab30ba5860c9d383