arm64: dts: rockchip: add RK3399-Q7 (Puma) SoM

The RK3399-Q7 SoM is a Qseven-compatible (70mm x 70mm, MXM-230
connector) system-on-module from Theobroma Systems, featuring the
Rockchip RK3399.

It provides the following feature set:
 * up to 4GB DDR3
 * on-module SPI-NOR flash
 * on-module eMMC (with 8-bit 1.8V interface)
 * SD card (on a baseboad) via edge connector
 * Gigabit Ethernet with on-module Micrel KSZ9031 GbE PHY
 * HDMI/eDP/2x MIPI-DSI
 * 2x MIPI-CSI
 * USB
   - 1x USB 3.0 dual-role (direct connection)
   - 2x USB 3.0 host + 1x USB 2.0 (on-module USB 3.0 hub)
 * on-module STM32 Cortex-M0 companion controller, implementing:
   - low-power RTC functionality (ISL1208 emulation)
   - fan controller (AMC6821 emulation)
   - USB<->CAN bridge controller
Signed-off-by: Klaus Goger <klaus.goger@theobroma-systems.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>