allow domain heap allocations to specify more than one NUMA node

allow domain heap allocations to specify more than one NUMA node

... using struct domain as a container for passing the respective
affinity mask: Quite a number of allocations are domain specific, yet
not to be accounted for that domain. Introduce a flag suppressing the
accounting altogether (i.e. going beyond MEMF_no_refcount) and use it
right away in common code (x86 and IOMMU code will get adjusted
subsequently).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>