iomap: fix submission side handling of completion side errors

iomap: fix submission side handling of completion side errors

The "if (dio->error)" in iomap_dio_bio_iter exists to stop submitting
more bios when a completion already return an error.  Commit cfe057f7db1f
("iomap_dio_actor(): fix iov_iter bugs") made it revert the iov by
"copied", which is very wrong given that we've already consumed that
range and submitted a bio for it.

Fixes: cfe057f7db1f ("iomap_dio_actor(): fix iov_iter bugs")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>