Fix dump when virtual display exists

SurfaceFlinger::getLayerSortedByZForHwcDisplay only worked for builtin
displays.

Bug: 8384764
Change-Id: I989275407fb2f06d166a6e70321c3211e27e562e
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 1017560..f0e6deb 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -122,7 +122,7 @@
 
     // for debugging only
     // TODO: this should be made accessible only to HWComposer
-    const Vector< sp<Layer> >& getLayerSortedByZForHwcDisplay(int disp);
+    const Vector< sp<Layer> >& getLayerSortedByZForHwcDisplay(int id);
 
 private:
     friend class Client;