Limit visibility of libmediametrics.so

Test: build
Bug: 138219814
Change-Id: I63a93d4d13e63ff364e9d5ca4a53316bd9770663

media/libmediametrics/Android.bp

@@ -42,6 +42,10 @@ cc_library_shared {
         enabled: true,
         symbol_file: "libmediametrics.map.txt",
     },
-}
-
 
+    visibility: [
+        "//frameworks/av:__subpackages__",
+        "//frameworks/base/core/jni",
+        "//frameworks/base/media/jni",
+    ],
+}