virtio-ccw: fix sanity check for vector

The commit 8dfbaa6ac ("virtio-ccw: introduce ccw specific queue limit")
did not touch the sanity check for the vector argument of the method
virtio_ccw_notify, despite intended as seen from
https://lists.nongnu.org/archive/html/qemu-devel/2015-04/msg02705.html
To be able to scale number of virtqueues using the constant this sanity
check needs to be altered.

Fixes: 8dfbaa6ac ("virtio-ccw: introduce ccw specific queue limit")
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
