scsi: ufs: Properly release resources if a task is aborted successfully

In current UFS task abort hook, namely ufshcd_abort(), if one task is
aborted successfully, clk_gating.active_reqs held by this task is not
decreased, which makes clk_gating.active_reqs stay above zero forever, thus
clock gating would never happen. Instead of releasing resources of one task
"manually", use the existing func __ufshcd_transfer_req_compl().  This
change also eliminates a possible race of scsi_dma_unmap() from the real
completion in IRQ handler path.

Link: https://lore.kernel.org/r/1596975355-39813-10-git-send-email-cang@codeaurora.org
Fixes: 1ab27c9c

 ("ufs: Add support for clock gating")
CC: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>