MIPS: Alchemy: Basic support for the DB1300 board.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2867/
Patchwork: https://patchwork.linux-mips.org/patch/2919/
Patchwork: https://patchwork.linux-mips.org/patch/2928/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>