Populate the lapics arrays and call cpu_add/lapic_create in the setup
phase instead. Also store the max APIC ID found in the newly
introduced max_apic_id global variable.

This is a requirement in order to make the static arrays currently
using MAX_LAPIC_ID dynamic.

Sponsored by:		Citrix Systems R&D
MFC after:		1 month
Reviewed by:		kib
Differential revision:	https://reviews.freebsd.org/D11911