cmsdk: Untangle internal vs. external dependencies

 * The public SDK build is currently including AIDLs which are
   meant to be used for internal purposes only. My assumption
   is that this particular implementation was done before we
   split off an "internal" SDK, which is used by the platform itself.
 * The issue came up when adding an AIDL which has a backing
   Java data object which was not included.
 * It should be safe to simply hide this interface. All references
   to it are hidden already. It is only used for internal purposes
   and does not change the API.
 * With the internal dependencies removed from the public SDK, we
   can completely remove the reference in the makefile.

Change-Id: I0515815543feb077ee5e289b9f900e28758c6e98