drm_hwcomposer: Set value for hdrOutputType for fake config

GetDisplayConfigurations_hasHdrType fails for headless displays since
the hdrOutputType is not initialized for fake modes. Set fake modes to
kSystem instead of kInvalid.

Change-Id: I051dc742b4786bbb0bf8a9384a6d3cde536eebce

hwc/HwcDisplayConfigs.cpp

@@ -76,6 +76,7 @@ void HwcDisplayConfigs::GenFakeMode(uint16_t width, uint16_t height) {
       .id = active_config_id,
       .group_id = 1,
       .mode = DrmMode(&headless_drm_mode_info),
+      .output_type = OutputType::kSystem,
   };
 
   mm_width = kHeadlessModeDisplayWidthMm;