scsi: ufs: core: Improve the struct ufs_hba documentation

Make the role of the structure members related to UIC command processing
more clear.

Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240912223019.3510966-2-bvanassche@acm.org


Reviewed-by: Bao D. Nguyen <quic_nguyenb@quicinc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>