qga: add memory block command that unsupported For memory block command, we only support for linux with sysfs. Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com> Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>