scsi: scsi_debug: Drop scsi_debug_device_reset() NULL pointer checks

scsi: scsi_debug: Drop scsi_debug_device_reset() NULL pointer checks

The SCSI cmnd pointer arg would never be NULL, so drop the check. In
addition, its SCSI device pointer would never be NULL (so drop that check
also).

The only caller is scsi_try_bus_device_reset(), and the command and its
device pointer could not be NULL when calling eh_device_reset_handler()
there.

Signed-off-by: John Garry <john.g.garry@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Link: https://lore.kernel.org/r/20230313093114.1498305-5-john.g.garry@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>