kernel/thread: Include thread-related enums within the kernel namespace

Previously, these were sitting outside of the Kernel namespace, which
doesn't really make sense, given they're related to the Thread class
which is within the Kernel namespace.

src/core/hle/service/sm/srv.cpp

@@ -101,7 +101,8 @@ void SRV::GetServiceHandle(Kernel::HLERequestContext& ctx) {
     // TODO(yuriks): Permission checks go here
 
     auto get_handle = [name, this](Kernel::SharedPtr<Kernel::Thread> thread,
-                                   Kernel::HLERequestContext& ctx, ThreadWakeupReason reason) {
+                                   Kernel::HLERequestContext& ctx,
+                                   Kernel::ThreadWakeupReason reason) {
         LOG_ERROR(Service_SRV, "called service={} wakeup", name);
         auto client_port = service_manager->GetServicePort(name);