changed serval-dna version from batphone-release-0.91 to commotion-wireless

To test:

build two nodes with the image, and ensure app advertising works and that one node can ping the other using servald.

Also enable olsrd-mdp and ensure the nodes have routes to each other.

Also also, check the memory usage of serval-dna. The memory leak fix probably won't make a difference, but it's worth checking.

If you would like images to test, I have them already built, just come find me.

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