scsi: ufs: core: Use str_true_false() helper in UFS_FLAG()

Remove hard-coded strings by using the str_true_false() helper function.

Signed-off-by: Liu Song <liu.song13@zte.com.cn>
Link: https://lore.kernel.org/r/20250721200138431dOU9KyajGyGi5339ma26p@zte.com.cn


Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>