scsi: ufs-mediatek: Introduce event_notify implementation

Introduce event_notify implementation on MediaTek UFS platform. A
vendor-specific tracepoint is added that can be used for debugging
purposes.

Link: https://lore.kernel.org/r/20201205115901.26815-5-stanley.chu@mediatek.com


Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>