wined3d: Don't compare texUnitMap entries to -1.
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 7aa4eb4..b905aea 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -1039,6 +1039,8 @@
 /*****************************************************************************
  * IWineD3DDevice implementation structure
  */
+#define WINED3D_UNMAPPED_STAGE ~0U
+
 struct IWineD3DDeviceImpl
 {
     /* IUnknown fields      */