wmi: Free the allocated acpi objects through wmi_get_event_data

These function allocate an acpi object by calling wmi_get_event_data, which
then calls acpi_evaluate_object, and it is not freed afterwards.

And kernel doc is fixed for parameters of wmi_get_event_data.

Signed-off-by: Anisse Astier <anisse@astier.eu>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
index 67f3fe7..6561dfc 100644
--- a/drivers/platform/x86/dell-wmi.c
+++ b/drivers/platform/x86/dell-wmi.c
@@ -238,6 +238,7 @@
 			input_sync(dell_wmi_input_dev);
 		}
 	}
+	kfree(obj);
 }