[Kernel] Use tables for export groups.

src/xenia/kernel/xam/xam_ui.cc

@@ -503,9 +503,8 @@ dword_result_t XamShowCommunitySessionsUI_entry(unknown_t r3, unknown_t r4) {
 }
 DECLARE_XAM_EXPORT1(XamShowCommunitySessionsUI, kNone, kStub);
 
-void RegisterUIExports(xe::cpu::ExportResolver* export_resolver,
-                       KernelState* kernel_state) {}
-
 }  // namespace xam
 }  // namespace kernel
 }  // namespace xe
+
+DECLARE_XAM_EMPTY_REGISTER_EXPORTS(UI);