scsi: ufs: Fix unsigned int compared with less than zero

Variable 'tag' is currently an unsigned int and is being compared to less
than zero, this check is always false. Fix this by making 'tag' an int.

Link: https://lore.kernel.org/r/20210806144301.19864-1-colin.king@canonical.com
Fixes: 4728ab4a

 ("scsi: ufs: Remove ufshcd_valid_tag()")
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Addresses-Coverity: ("Macro compares unsigned to 0")