Support virtqueue creation(enablement) after DRIVER_OK stage

[Parav Pandit]

Currently, a virtqueue must be enabled before driver has set the
DRIVER_OK status bit.

spec citation to section "Driver Requirements: Device Initialization"

"Perform device-specific setup, including discovery of virtqueues
for the device, optional per-bus setup, reading and possibly writing
the deviceâs virtio configuration space, and population of virtqueues."

This implies that a virtqueue must be enabled before reaching the
DRIVER_OK stage. There was no explicit mention about ability to
enable the virtqueue after DRIVER_OK stage.

In following use cases, creating a virtqueue after DRIVER_OK phase is
desired.

Use cases:

1. Dynamically create aq when administrative commands to be used.
2. Dynamically create the net device tx/rxq when device is
   opened when deploying for a container.
   In a container, number of virtqueues to be used may be <= max queues.
3. Dynamically create flow filter queues of netdevice when
   ARFS or ethtool filters are enabled as listed in [1].
4. Dynamically create rtc functionality related read virtqueue only
   when net device when time stamping to be used.
5. When XDP program is set, one can create additional XDP specific
   queues without affecting existing queues.

Solution:
https://lists.oasis-open.org/archives/virtio-comment/202310/msg00183.html
Patches link for automation:
https://lore.kernel.org/virtio-comment/[e-mail]/T/#t