MIPS: pistachio: Add an initial defconfig

Add a defconfig for Pistachio which enables drivers for all the
currently supported peripherals on the SoC.

Signed-off-by: Govindraj Raja <govindraj.raja@imgtec.com>
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: James Hartley <james.hartley@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/9570/


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