HWC2: Add getHdrCapabilities stub to adapter

Adds a minimal getHdrCapabilities stub to the HWC2On1Adapter, which
always returns 0 supported HDR types (as per the HWC2 spec).

Bug: 25684127
Change-Id: I472ad9f08d1b97d5de69d044790badf3af60da72
diff --git a/services/surfaceflinger/DisplayHardware/HWC2On1Adapter.h b/services/surfaceflinger/DisplayHardware/HWC2On1Adapter.h
index bffeefe..6fdb184 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2On1Adapter.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2On1Adapter.h
@@ -194,6 +194,9 @@
             HWC2::Error getConfigs(uint32_t* outNumConfigs,
                     hwc2_config_t* outConfigIds);
             HWC2::Error getDozeSupport(int32_t* outSupport);
+            HWC2::Error getHdrCapabilities(uint32_t* outNumTypes,
+                    int32_t* outTypes, float* outMaxLuminance,
+                    float* outMaxAverageLuminance, float* outMinLuminance);
             HWC2::Error getName(uint32_t* outSize, char* outName);
             HWC2::Error getReleaseFences(uint32_t* outNumElements,
                     hwc2_layer_t* outLayers, int32_t* outFences);