dm verity: fix DM_VERITY_OPTS_MAX value

Three optional parameters must be accepted at once in a DM verity table, e.g.:
  (verity_error_handling_mode) (ignore_zero_block) (check_at_most_once)
Fix this to be possible by incrementing DM_VERITY_OPTS_MAX.

Signed-off-by: JeongHyeon Lee <jhs2.lee@samsung.com>
Fixes: 843f38d3 ("dm verity: add 'check_at_most_once' option to only validate hashes once")
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>