MIPS: DTS: img: add device tree for Marduk board

MIPS: DTS: img: add device tree for Marduk board

Add support for Imagination Technologies' Marduk board which is based
on Pistachio SoC. It is also known as Creator Ci40. Marduk is legacy
name and will be there for decades.

Documentation for this board can be found on
https://docs.creatordev.io/ci40/

This patch adds initial support for board with following peripherals:

* PWM based heartbeat LED
* GPIO based buttons
* SPI NOR flash on SPI1
* UART0 and UART1
* SD card
* Ethernet
* USB
* PWM
* ADC
* I2C

Signed-off-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: James Hartley <james.hartley@imgtec.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14394/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>