Add vts case for OverlayProperties#isMixedColorSpacesSupported.

 - add sRGB and DisplayP3 layers in HWC, if mixedColorSpaces is
   supported, only DPU composition happens.

Bug: 311252937
Test: this
Change-Id: I400a6dd18a05bbdf69e249907e13a4fa7eafbf01
diff --git a/graphics/composer/aidl/vts/ReadbackVts.cpp b/graphics/composer/aidl/vts/ReadbackVts.cpp
index c72ec69..283b8ce 100644
--- a/graphics/composer/aidl/vts/ReadbackVts.cpp
+++ b/graphics/composer/aidl/vts/ReadbackVts.cpp
@@ -67,8 +67,9 @@
         case ColorMode::DISPLAY_P3:
             return Dataspace::DISPLAY_P3;
         case ColorMode::SRGB:
+            return Dataspace::SRGB;
         default:
-            return common::Dataspace::UNKNOWN;
+            return Dataspace::UNKNOWN;
     }
 }