Add DecoderRenderTest to tv-postsubmit

Bug: 336350963
Test: atest DecoderRenderTest across a variety of TV devices
Change-Id: Id893414f7d4b7b28ab18c06a88429185e855ec66
diff --git a/media/TEST_MAPPING b/media/TEST_MAPPING
index cd5d354..d388596 100644
--- a/media/TEST_MAPPING
+++ b/media/TEST_MAPPING
@@ -44,5 +44,11 @@
             ],
             "file_patterns": ["(?i)drm|crypto"]
         }
+    ],
+    // Postsubmit tests for TV devices
+    "tv-postsubmit": [
+       {
+           "name": "DecoderRenderTest"
+       }
     ]
 }