MIPS: Alchemy: Add basic support for the GPR board

From: Wolfgang Grandegger <wg@denx.de>

Add basic support for the General Purpose Router (GPR) board from
Trapeze ITS.

Signed-off-by: Wolfgang Grandegger <wg@denx.de>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1460/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>