The quark branch is still work in progress, so it may not compile, and it won't use GPUs.
If you want to use multi-gpus branch, you should use StarPU scheduler. A new version of MAGMA is in development to introduce a cmake compilation process, that will ease the compilation of the this library.
Concerning the axpy problem, it's due to a renaming of the function in PLASMA from axpy to geadd. A simple sed to replace the name in MAGMA should fix it.
Again, this work has been released too soon and is right now, not really user friendly. We are working on this, so that everyone can benefit from it.