scsi: sd: Clear sdkp->protection_type if disk is reformatted without PI

If an attached disk with protection information enabled is reformatted
to Type 0 the revalidation code does not clear the original protection
type and subsequent accesses will keep setting RDPROTECT/WRPROTECT.

Set the protection type to 0 if the disk reports PROT_EN=0 in READ
CAPACITY(16).

[mkp: commit desc]

Fixes: fe542396

 ("[SCSI] sd: Ensure we correctly disable devices with unknown protection type")
Link: https://lore.kernel.org/r/1578532344-101668-1-git-send-email-chenxiang66@hisilicon.com
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>