scsi: ufs: Fix unexpected values from ufshcd_read_desc_param()

scsi: ufs: Fix unexpected values from ufshcd_read_desc_param()

[ Upstream commit 1699f980d87fb678a669490462cf0b9517c1fb47 ]

WB-related sysfs entries can be accessed even when an UFS device does not
support the feature. The descriptors which are not supported by the UFS
device may be wrongly reported when they are accessed from their
corrsponding sysfs entries. Fix it by adding a sanity check of parameter
offset against the actual decriptor length.

Link: https://lore.kernel.org/r/1603346348-14149-1-git-send-email-cang@codeaurora.org
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Acked-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>