MIPS: dts: qca: introduce AR9331 devicetree

MIPS: dts: qca: introduce AR9331 devicetree

This patch introduces devicetree for Atheros AR9331 SoC (AKA Hornet).
The AR9331 chip is a Wi-Fi System-On-Chip (WiSOC),
typically used in very cheap Access Points and Routers.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Cc: Gabor Juhos <juhosg@openwrt.org>
Cc: Alban Bedel <albeu@free.fr>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12878/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>