x86: fix build breakage on voyage

Impact: build fix

x86_cpu_to_apicid and x86_bios_cpu_apicid aren't defined for voyage.
Earlier patch forgot to conditionalize early percpu clearing.  Fix it.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Tejun Heo <tj@kernel.org>