threading: handle device commands in GetInstanceProcAddr

Call layer_intercept_proc in GetInstanceProcAddr.
diff --git a/layers/threading.cpp b/layers/threading.cpp
index db5f6ae..c97722e 100644
--- a/layers/threading.cpp
+++ b/layers/threading.cpp
@@ -236,6 +236,8 @@
     layer_data *my_data;
 
     addr = layer_intercept_instance_proc(funcName);
+    if (!addr)
+        addr = layer_intercept_proc(funcName);
     if (addr) {
         return addr;
     }