Add inputflinger_tests to staged platinum config

This was requested after the review of the postmortem of a crash in
InputDispatcher.

Bug: 318078782
Test: (cd frameworks/native/services/inputflinger && atest)
Change-Id: I937375c3988a0065b0dfb9cec0d7e345e016f723
diff --git a/services/inputflinger/TEST_MAPPING b/services/inputflinger/TEST_MAPPING
index 513cbfa..293ad66 100644
--- a/services/inputflinger/TEST_MAPPING
+++ b/services/inputflinger/TEST_MAPPING
@@ -285,5 +285,10 @@
     {
       "name": "CtsInputHostTestCases"
     }
+  ],
+  "staged-platinum-postsubmit": [
+    {
+      "name": "inputflinger_tests"
+    }
   ]
 }