x86, apic: Remove smp_callin_clear_local_apic callback

Since commit b5660ba7 ("x86, platforms: Remove NUMAQ") removed NUMAQ,
the smp_callin_clear_local_apic() apic callback has been obsolete.
Remove it.

Signed-off-by: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1407302349040.17503@chino.kir.corp.google.com


Signed-off-by: H. Peter Anvin <hpa@zytor.com>