block: convert to errseq_t based writeback error tracking

This is a very minimal conversion to errseq_t based error tracking
for raw block device access. Just have it use the standard
file_write_and_wait_range call.

Note that there are internal callers that call sync_blockdev
and the like that are not affected by this. They'll continue
to use the AS_EIO/AS_ENOSPC flags for error reporting like
they always have for now.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJeff Layton <jlayton@redhat.com>

fs/block_dev.c

@@ -624,7 +624,7 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	struct block_device *bdev = I_BDEV(bd_inode);
 	int error;
 	
-	error = filemap_write_and_wait_range(filp->f_mapping, start, end);
+	error = file_write_and_wait_range(filp, start, end);
 	if (error)
 		return error;