isapc: Remove unnecessary migration compatibility code

isapc: Remove unnecessary migration compatibility code

We don't touch isapc when we change guest ABI and add new entries
to PC_COMPAT_* or new PCMachineClass compat flags.  This means
isapc never guaranteed guest ABI and cross-QEMU-version live
migration compatibility.  There's no point in keeping code for
kvm-pv-eoi and APIC ID compatibility in pc_init_isa().

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>