x86: call early_cpu_init at the same point

Call early_cpu_init() at the same (early) point in setup_arch().
The x86_64 code was calling it relatively late, after when other arch
code need to do cpu-related setup which depends on it.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>