Drop message byte setting if the host byte is already set, and translate
message bytes into the related host bytes when evaluating an overrun or
underrun.

Link: https://lore.kernel.org/r/20210427083046.31620-20-hare@suse.deReviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>