scsi: ufs: flush eh_work when eh_work scheduled.

Forget a condition: eh_work scheduled but do not start to work.

Signed-off-by: Zang Leigang <zangleigang@hisilicon.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>