Use library exported headers, not raw path

Bug: 147679485
Test: build
Change-Id: I8146ca4302225c4d05d841616c3e3548c673827d
diff --git a/src/jni/rtp/Android.bp b/src/jni/rtp/Android.bp
index b6c8588..b933054 100644
--- a/src/jni/rtp/Android.bp
+++ b/src/jni/rtp/Android.bp
@@ -45,10 +45,6 @@
         "libstagefright_amrnbdec",
         "libstagefright_amrnbenc",
     ],
-    include_dirs: [
-        "frameworks/av/media/libstagefright/codecs/amrnb/enc/src",
-        "frameworks/av/media/libstagefright/codecs/amrnb/dec/src",
-    ],
     cflags: [
         "-fvisibility=hidden",
         "-Wall",