vdpasim: Off by one in vdpasim_set_group_asid()

The > comparison needs to be >= to prevent an out of bounds access
of the vdpasim->iommu[] array.  The vdpasim->iommu[] is allocated in
vdpasim_create() and it has vdpasim->dev_attr.nas elements.

Fixes: 87e5afeac247 ("vdpasim: control virtqueue support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Message-Id: <YotGQU1q224RKZR8@kili>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>