scsi: esp_scsi: Grant disconnect privilege for untagged commands

A SCSI device is not granted disconnect privilege by an esp_scsi host
unless that device has its simple_tags flag set. However, a device may
support disconnect/reselect and not support command queueing. Allow such
devices to disconnect and thereby improve bus utilization.

Drop the redundant 'lp' check. The mid-layer invokes .slave_alloc and
.slave_destroy in such a way that we may rely on scmd->device->hostdata
for as long as scmd belongs to the low-level driver.

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>