libdl: Rename LIBC_PRIVATE to LIBC_PLATFORM

Bug: http://b/26386014
Change-Id: I3255faac66a96867aed302e205e3644b40ce7750
diff --git a/libdl/libdl.arm.map b/libdl/libdl.arm.map
index b9e494a..aa6907a 100644
--- a/libdl/libdl.arm.map
+++ b/libdl/libdl.arm.map
@@ -21,7 +21,7 @@
     dlvsym;
 } LIBC;
 
-LIBC_PRIVATE {
+LIBC_PLATFORM {
   global:
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;