Revert "virtio: improve virtio devices initialization time"

Revert "virtio: improve virtio devices initialization time"

This reverts commit 6f0bb230722931d17fb284eee8efd40b9d653822.

This reverts commit f87d72f5c5bff0837d409a56bd34f439a90119ca as that is
reported to break cleanup and migration.

Cc: Gal Hammer <ghammer@redhat.com>
Cc: Sitong Liu <siliu@redhat.com>
Cc: Xiaoling Gao <xiagao@redhat.com>
Suggested-by: Greg Kurz <groug@kaod.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Reported-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>