iomap: support T10 protection information

iomap: support T10 protection information

Add support for generating / verifying protection information in iomap.
This is done by hooking into the bio submission and then using the
generic PI helpers.  Compared to just using the block layer auto PI
this extends the protection envelope and also prepares for eventually
passing through PI from userspace at least for direct I/O.

To generate or verify PI, the file system needs to set the
IOMAP_F_INTEGRITY flag on the iomap for the request, and ensure the
ioends are used for all integrity I/O.  Additionally the file system
should defer read I/O completions to user context so that the guard
tag validation isn't run from interrupt context.

Signed-off-by: Christoph Hellwig <hch@lst.de>