scsi: ufs: core: Flush exception handling work when RPM level is zero

scsi: ufs: core: Flush exception handling work when RPM level is zero

Ensure that the exception event handling work is explicitly flushed during
suspend when the runtime power management level is set to UFS_PM_LVL_0.

When the RPM level is zero, the device power mode and link state both
remain active. Previously, the UFS core driver bypassed flushing exception
event handling jobs in this configuration. This created a race condition
where the driver could attempt to access the host controller to handle an
exception after the system had already entered a deep power-down state,
resulting in a system crash.

Explicitly flush this work and disable auto BKOPs before the suspend
callback proceeds. This guarantees that pending exception tasks complete
and prevents illegal hardware access during the power-down sequence.

Fixes: 57d104c153d3 ("ufs: add UFS power management support")
Signed-off-by: Thomas Yen <thomasyen@google.com>
Cc: Stable Tree <stable@vger.kernel.org>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/20260129165156.956601-1-thomasyen@google.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>