qapi: make visit_type_size fallback to type_int

Currently visit_type_size checks if the visitor's type_size function pointer is
NULL. If not, it calls it, otherwise it calls v->type_uint64(). But neither of
these pointers are ever set. Fallback to calling v->type_int() in this third
(default) case.

Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Message-id: 1375109277-25561-6-git-send-email-imammedo@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
