dm-integrity: Do not emit journal configuration in DM table for Inline mode

The Inline mode does not use a journal; it makes no sense to print
journal information in DM table. Print it only if the journal is used.

The same applies to interleave_sectors (unused for Inline mode).

Also, add comments for arg_count, as the current calculation
is quite obscure.

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>