linux-phytec-fsl

block: Ensure we only enable integrity metadata for reads and writes

We'd occasionally attempt to generate protection information for flushes
and other requests with a zero payload. Make sure we only attempt to
enable integrity for reads and writes.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>