virDomainMemoryDefValidate: Fix VIRTIO_MEM alignment check

virDomainMemoryDefValidate: Fix VIRTIO_MEM alignment check

Inside of virDomainMemoryDefValidate() there's a check that
address where a virtio-mem memory device is mapped to is a
multiple of its block size. But this check is off by a couple of
bits, because the memory address is in bytes while the block size
is in kibibytes. Therefore, when checking whether address is a
multiple of the block size, the latter has to be multiplied by a
factor of 1024.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>