unmaintained/samsung-a5(u)lte-downstream: new device (Samsung Galaxy A5)

Like the other unmaintained MSM8916 device ports, this is just for testing things on the downstream kernel (which is useful sometimes for mainline work). This is pretty much untested, but samsung-a5ulte-downstream boots to Weston at least with USB working.

I also added a samsung-a5lte-downstream that is set up similarly. This one is completely untested, I added it for @minlexx who mentioned this might be useful to get brightness control working on mainline. :)