socktap: Adding the Autotalks link layer

[khevessy]

This adds Autotalks link layer to the socktap example, working on both Craton and Secton devices. Links with Autotalks libraries. Also adds possibility to build for Craton (cross-compilation for ARM using the toolchain supplied with Autotalks SDK).

Initialization of the device can be taken from the Autotalks example, as I propose in the documentation page (I used almost exactly their code, therefore I think it cannot be in the library).

I should add that my knowledge of CMake is not great, so that part may require some further work.

[khevessy]

I am not sure if you are happy with user manually creating the symbolic link to SDK root as mentioned above, but to me it seems good enough (as the path is not defined exactly by Autotalks). Apart from that I hopefully solved all your requests.

[khevessy]

Note that socktap now does not work as stated here. After recent security changes, it cannot be compiled in the base repository either.

[riebl]

Sorry, I did not notice that socktap cannot be compiled. I should add socktap to the CI! Are you also suffering from the assertion failure mentioned by @lo-hei?

[riebl]

Thanks for your hard work and patience @khevessy!

[khevessy]

After your fix, I've tried socktap on Secton and Craton and it is working well.