scsi: qla2xxx: Fix device staying in blocked state

This patch fixes issue reported by some of the customers, who discovered
that after cable pull scenario the devices disappear and path seems to
remain in blocked state. Once the device reappears, driver does not seem to
update path to online. This issue appears because of the defer flag
creating race condition where the same session reappears.  This patch fixes
this issue by indicating SCSI-ML of device lost when
qlt_free_session_done() is called from qlt_unreg_sess().

Fixes: 41dc529a ("qla2xxx: Improve RSCN handling in driver")
Signed-off-by: Quinn Tran <qtran@marvell.com>
Cc: stable@vger.kernel.org #4.19
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>