iomap: inline iomap_dio_bio_opflags()

It is neater to build blk_opf_t fully in one place, so inline
iomap_dio_bio_opflags() in iomap_dio_bio_iter().

Also tidy up the logic in dealing with IOMAP_DIO_CALLER_COMP, in generally
separate the logic in dealing with flags associated with reads and writes.

Originally-from: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20250320120250.4087011-2-john.g.garry@oracle.com


Signed-off-by: Christian Brauner <brauner@kernel.org>