fix fs-integrity for non-PI metadata v2

Hi all,

this series fixes incorrect calls into the PI generation helpers
when using fs-integrity on devics with non-PI metadata.

Changes since v1:
 - fix two more null pointer dereferences

(I though I already sent this out yesterday, but can't find it in the
archives.  At least this way I could pick up two more reviews from the
post as part of the larger lazy bounce buffer series.  Sorry if you
somehow got this twice)

Diffstat:
 block/bio-integrity-auto.c    |   10 ++--------
 block/bio-integrity-fs.c      |    6 +++++-
 fs/iomap/bio.c                |    2 +-
 include/linux/bio-integrity.h |    3 +++
 4 files changed, 11 insertions(+), 10 deletions(-)