Move libnl headers to their own project

Change-Id: If3f20575507431afa7a79aee6b99823a2d1df324
diff --git a/libnl_2/Android.mk b/libnl_2/Android.mk
index 800c2b2..1fbde21 100644
--- a/libnl_2/Android.mk
+++ b/libnl_2/Android.mk
@@ -14,7 +14,7 @@
         socket.c
 
 LOCAL_C_INCLUDES += \
-        $(LOCAL_PATH)/include
+        external/libnl-headers
 
 # Static Library
 LOCAL_MODULE := libnl_2