DisplayDevice: initialize mDisplayToken correctly

mDisplayToken should be initialized by displayToken.

Change-Id: I0a5fec1f1732200a32d10b1575239dceffe6dee4
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index ce98b67..69b9c34 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -77,6 +77,7 @@
         EGLConfig config)
     : mFlinger(flinger),
       mType(type), mHwcDisplayId(-1),
+      mDisplayToken(displayToken),
       mNativeWindow(nativeWindow),
       mFramebufferSurface(framebufferSurface),
       mDisplay(EGL_NO_DISPLAY),