dm-integrity: introduce the Inline mode

This commit introduces a new 'I' mode for dm-integrity.

The 'I' mode may be selected if the underlying device has non-power-of-2
sector size. In this mode, dm-integrity will store integrity data
directly in device's sectors and it will not use journal.

This mode improves performance and reduces flash wear because there would
be no journal writes.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>