libxl: fix population of the online vCPU bitmap for PVH

libxl: fix population of the online vCPU bitmap for PVH

libxl passes some information to libacpi to create the ACPI table for a PVH
guest, and among that information it's a bitmap of which vCPUs are online
which can be less than the maximum number of vCPUs assigned to the domain.

While the population of the bitmap is done correctly for HVM based on the
number of online vCPUs, for PVH the population of the bitmap is done based on
the number of maximum vCPUs allowed.  This leads to all local APIC entries in
the MADT being set as enabled, which contradicts the data in xenstore if vCPUs
is different than maximum vCPUs.

Fix by copying the internal libxl bitmap that's populated based on the vCPUs
parameter.

Reported-by: Arthur Borsboom <arthurborsboom@gmail.com>
Link: https://gitlab.com/libvirt/libvirt/-/issues/399
Reported-by: Leigh Brown <leigh@solinno.co.uk>
Fixes: 14c0d328da2b ('libxl/acpi: Build ACPI tables for HVMlite guests')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Tested-by: Leigh Brown <leigh@solinno.co.uk>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>