Move linker-namespace functions to LIBC_PLATFORM

Bug: http://b/28174921
Change-Id: I089dbeeea813fc2128b9c2f6268a578d23a1954a
diff --git a/libdl/libdl.arm.map b/libdl/libdl.arm.map
index 9d97bd0..2821509 100644
--- a/libdl/libdl.arm.map
+++ b/libdl/libdl.arm.map
@@ -16,8 +16,6 @@
 
 LIBC_N {
   global:
-    android_init_namespaces;
-    android_create_namespace;
     dlvsym;
 } LIBC;
 
@@ -28,4 +26,6 @@
     android_set_application_target_sdk_version;
     android_get_LD_LIBRARY_PATH;
     android_update_LD_LIBRARY_PATH;
+    android_init_namespaces;
+    android_create_namespace;
 } LIBC_N;