block: fix blk_integrity_register to use template's interval_exp if not 0

block: fix blk_integrity_register to use template's interval_exp if not 0

When registering an integrity profile: if the template's interval_exp is
not 0 use it, otherwise use the ilog2() of logical block size of the
provided gendisk.

This fixes a long-standing DM linear target bug where it cannot pass
integrity data to the underlying device if its logical block size
conflicts with the underlying device's logical block size.

Cc: [email protected]
Reported-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Acked-by: Martin K. Petersen <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>