x32: Drop non-__vdso weak symbols from the x32 VDSO

Drop the legacy weak symbols that don't carry the __vdso prefix from
the x32 VDSO.  This is a new ABI and we don't need to support that
legacy; the actual libc will export the proper symbols.

Suggested-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/4F42E171.9080005@mit.edu


Cc: H. J. Lu <hjl.tools@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>