iomap: standardize tracepoint formatting and storage

Print all the offset, pos, and length quantities in hexadecimal.  While
we're at it, update the types of the tracepoint structure fields to
match the types of the values being recorded in them.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>