sunrpc: Remove hidden aliases for global data symbols (bug 26210)

It is generally not possible to add hidden aliases for global data
symbols: If the main executable contains a copy relocation against
the symbol, the hidden aliases keep pointing to the glibc-internal
copy of the symbol, instead of the symbol actually used by the
application.

Fixes commit 89aacb51 ("sunrpc:
Remove stray exports without --enable-obsolete-rpc [BZ #23166]").

Reviewed-by: Carlos O'Donell <carlos@redhat.com>