MAINTAINERS: change Loic as wcn36xx maintainer

I don't have time for being wcn36xx maintainer but Loic is willing to step up.
Thanks Loic!

Also remove Eugene's old tree, it has not been used for a long time.

Signed-off-by: Kalle Valo <kvalo@kernel.org>
Acked-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220128135841.1926-2-kvalo@kernel.org