s390-bios: Extend find_dev() for non-virtio devices

s390-bios: Extend find_dev() for non-virtio devices

We need a method for finding the subchannel of a dasd device. Let's
modify find_dev to handle this since it mostly does what we need. Up to
this point find_dev has been specific to only virtio devices.

Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
Acked-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <1554388475-18329-11-git-send-email-jjherne@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>