apic is not acpi, although they are acronyms. Due to a confusion of 
mine, those things were mixed, leading to a bug reported at
https://sourceforge.net/tracker/index.php?func=detail&aid=1903732&group_id=180599&atid=893831

This patch fixes it, by assigning smp_cpus instead of MAX_CPUS to 
lapic_id in the MP APIC tables.

Signed-off-by: Glauber Costa <gcosta@redhat.com>