vhost/scsi: Global tcm_vhost -> vhost_scsi rename

There is a large amount of code that still references the original
'tcm_vhost' naming conventions, instead of modern 'vhost_scsi'.

Go ahead and do a global rename to make the usage consistent.

Cc: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>