vdpa/mlx5: Setup driver only if VIRTIO_CONFIG_S_DRIVER_OK

vdpa/mlx5: Setup driver only if VIRTIO_CONFIG_S_DRIVER_OK

set_map() is used by mlx5 vdpa to create a memory region based on the
address map passed by the iotlb argument. If we get successive calls, we
will destroy the current memory region and build another one based on
the new address mapping. We also need to setup the hardware resources
since they depend on the memory region.

If these calls happen before DRIVER_OK, It means that driver VQs may
also not been setup and we may not create them yet. In this case we want
to avoid setting up the other resources and defer this till we get
DRIVER OK.

Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20200908123346.GA169007@mtl-vdi-166.wap.labs.mlnx
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>