mptable - use the table's cpu_flags

mptable - use the table's cpu_flags

 * Sometimes the CPUs are marked as disabled in the APIC table, and for
   good reason (e.g. a machine having only 24 cores, but 32 appearing in
   the APIC table, 8 of them disabled).

 * Just in case, provide an override that falls back to the old
   behaviour. This is the tunable hw.lapic_force_enable. It will force
   all lapic entries to be marked as enabled. It is however not the
   default.

 * When parsing, don't error out when a lapic id is invalid (255) but it
   is disabled.

Reported-by: Mihai Carabas, Francois Tigeot