x86: Remove unused atomics

x86: Remove unused atomics

Remove unused atomics from <sysdeps/x86/atomic-machine.h>.

The resulting libc.so is identical on both x86_64 and
i386 targets compared to unpatched builds:

$ sha1sum libc-x86_64-old.so libc-x86_64-new.so
b89aaa2b71efd435104ebe6f4cd0f2ef89fcac90  libc-x86_64-old.so
b89aaa2b71efd435104ebe6f4cd0f2ef89fcac90  libc-x86_64-new.so
$ sha1sum libc-i386-old.so libc-i386-new.so
aa70f2d64da2f0f516634b116014cfe7af3e5b1a  libc-i386-old.so
aa70f2d64da2f0f516634b116014cfe7af3e5b1a  libc-i386-new.so

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cc: Collin Funk <collin.funk1@gmail.com>
Cc: H.J.Lu <hjl.tools@gmail.com>
Cc: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>