Add TEST_MAPPING for input-related code

For better presubmit coverage, include all input-related code into
TEST_MAPPING files.

Bug: 167947085
Test: cd frameworks/native/services/inputflinger && atest

Change-Id: I7ba46c872c917deb8dfc0c17be4662b9caeacf13
diff --git a/libs/input/TEST_MAPPING b/libs/input/TEST_MAPPING
new file mode 100644
index 0000000..9626d8d
--- /dev/null
+++ b/libs/input/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "imports": [
+    {
+      "path": "frameworks/native/services/inputflinger"
+    }
+  ]
+}