scsi: ufs: Use generic error code in ufshcd_set_dev_pwr_mode()

The return value of ufshcd_set_dev_pwr_mode() is passed to device PM
core. However, the function currently returns a SCSI result which the PM
core doesn't understand.  This might lead to unexpected behaviors in
userland; a platform reset was observed in Android.

Use a generic error code for SSU failures.

Link: https://lore.kernel.org/r/1642743182-54098-1-git-send-email-kwmad.kim@samsung.com


Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Kiwoong Kim <kwmad.kim@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>