[XEN] Replace hvm_setup_platform() with hvm_domain_initialise()

and extra code in hvm_vcpu_initialise(). Remove 'apic' config
option -- HVM CPUs will always have an APIC (which should be
set up in virtual wire mode for backward compatibility, just as
in a real system).
Signed-off-by: Keir Fraser <keir@xensource.com>

tools/python/README.XendConfig

@@ -123,7 +123,6 @@ otherConfig
                                 image.hvm.vncconsole
                                 image.hvm.pae
                                 image.hvm.acpi (also in image.devices)
-                                image.hvm.apic
                                 image.hvm.devices.boot
                                 image.hvm.devices.fda
                                 image.hvm.devices.fdb