scsi: ufs: core: Add debugfs attributes for triggering the UFS EH

Make it easier to test the impact of the UFS error handler on software that
submits SCSI commands to the UFS driver.

Link: https://lore.kernel.org/r/20211020214024.2007615-8-bvanassche@acm.org


Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>