scsi: ufs: core: Fix single doorbell mode support

scsi: ufs: core: Fix single doorbell mode support

Commit 22089c218037 ("scsi: ufs: core: Optimize the hot path")
accidentally broke support for the legacy single doorbell mode.  The
tag_set.shared_tags pointer is only != NULL if shared tag support is
enabled. The UFS driver only enables shared tag support in MCQ mode.

Fix this by handling legacy and MCQ modes differently in
ufshcd_tag_to_cmd().

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Closes: https://lore.kernel.org/linux-scsi/c988a6dd-588d-4dbc-ab83-bbee17f2a686@samsung.com/
Reported-by: André Draszik <andre.draszik@linaro.org>
Closes: https://lore.kernel.org/linux-scsi/83ffbceb9e66b2a3b6096231551d969034ed8a74.camel@linaro.org/
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: 22089c218037 ("scsi: ufs: core: Optimize the hot path")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: André Draszik <andre.draszik@linaro.org>
Link: https://patch.msgid.link/20251114193406.3097237-1-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>