arm64: dts: marvell: add Device Tree files for Armada-8KP

This commit adds the base Device Tree files for the Armada 8KPlus.
The Armada 8KP SoCs include several hardware blocks, and this
commit only adds support for the AP810 block, that contains the CPU
core and basic peripherals.

AP810 is a high-performance die, includes octal core application
processor based ARMv8-A architecture, two standard high speed DDR4
interface, and GIC-600 interrupt controller.
AP810 Built as part of Marvell’s MoChi AP family products.

Armada-8080 (8KPlus family), include an AP810 block that contains
the CPU core and basic peripherals.

This commit creates the following hierarchy:
 * armada-ap810-ap0.dtsi - definitions common to AP810
 	* armada-ap810-ap0-octa-core.dtsi - description of the octa cores
		* armada-8080.dtsi - description of the 8080 SoC
			* armada-8080-db.dts - description of the 8080 board

Signed-off-by: Hanna Hawa <hannah@marvell.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>