hostmem: add properties for NUMA memory policy

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
[Raise errors on setting properties if !CONFIG_NUMA.  Add BUILD_BUG_ON
 checks. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>