btrfs: remove the return value from submit_uncompressed_range

The return value from submit_uncompressed_range is ignored, and that's
fine because the error reporting happens through the mapping and
ordered_extent.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>