scsi: ufs: fix failure to read the string descriptor

commit bde44bb665d049468b6a1a2fa7d666434de4f83f upstream.

While reading variable size descriptors (like string descriptor), some UFS
devices may report the "LENGTH" (field in "Transaction Specific fields" of
Query Response UPIU) same as what was requested in Query Request UPIU
instead of reporting the actual size of the variable size descriptor.
Although it's safe to ignore the "LENGTH" field for variable size
descriptors as we can always derive the length of the descriptor from
the descriptor header fields. Hence this change impose the length match
check only for fixed size descriptors (for which we always request the
correct size as part of Query Request UPIU).

Reviewed-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[Wei Li: Slight tweaks to get the cherry-pick to apply,resolved collisions.]
Signed-off-by: Li Wei <liwei213@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>