realtek: update the tree to the latest refactored version

* rename the target to realtek
* add refactored DSA driver
* add latest gpio driver
* lots of arch cleanups
* new irq driver
* additional boards

Signed-off-by: Bert Vermeulen <bert@biot.com>
Signed-off-by: Birger Koblitz <mail@birger-koblitz.de>
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: John Crispin <john@phrozen.org>