Add initial support for boards based on the Imagination Pistachio SoC.
Pistachio is based on a dual-core MIPS interAptiv CPU and will boot
using device-tree.

Signed-off-by: James Hartley
Signed-off-by: Andrew Bresticker
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: Ezequiel Garcia
Cc: James Hogan
Patchwork: https://patchwork.linux-mips.org/patch/9569/
Signed-off-by: Ralf Baechle