xl: correct xl cpupool-numa-split with vcpu limited dom0

xl: correct xl cpupool-numa-split with vcpu limited dom0

When trying to use xl cpupool-numa-split and dom0 is limited to less
vcpus than one numa node the operation will fail.

Correct this by allowing this configuration.

Reported-by: Glenn Enright <glenn@rimuhosting.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
(cherry picked from commit c256d2afc1cad0cca912492e338d6ff97e477c4f)
(cherry picked from commit 78a30103813a7929e922de7414cc56fa2ae52984)
(cherry picked from commit f8972b4223ee76800afa13432403daf248b46805)