intel_th: Fix a deadlock in modprobing

Driver initialization tries to request a hub (GTH) driver module from
its probe callback, resulting in a deadlock.

This patch solves the problem by adding a deferred work for requesting
the hub module.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: <stable@vger.kernel.org> # 4.4.x-
diff --git a/drivers/hwtracing/intel_th/intel_th.h b/drivers/hwtracing/intel_th/intel_th.h
index 0df22e3..0482848 100644
--- a/drivers/hwtracing/intel_th/intel_th.h
+++ b/drivers/hwtracing/intel_th/intel_th.h
@@ -205,6 +205,9 @@
 
 	int			id;
 	int			major;
+#ifdef CONFIG_MODULES
+	struct work_struct	request_module_work;
+#endif /* CONFIG_MODULES */
 #ifdef CONFIG_INTEL_TH_DEBUG
 	struct dentry		*dbg;
 #endif