target-i386: Set APIC ID using cpu_index on CONFIG_USER

target-i386: Set APIC ID using cpu_index on CONFIG_USER

The PC CPU initialization code already sets apic-id based on the CPU
topology, and CONFIG_USER doesn't need the topology-based APIC ID
calculation code.

Make CONFIG_USER set apic-id before realizing the CPU (just like PC
already does), so we can simplify x86_cpu_initfn later. As there is no
CPU topology configuration in CONFIG_USER, just use cpu_index as the
APIC ID.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>