hi846: minor config updates
this should fix things pointed out in comments from https://lore.kernel.org/linux-media/20210708125424.GY3@valkosipuli.retiisi.eu/ and https://lore.kernel.org/linux-media/20210708125729.GZ3@valkosipuli.retiisi.eu/
review is much appreciated. I haven't yet sent this as an answer.