arm64: dts: allwinner: h618: add Transpeed 8K618-T TV box

arm64: dts: allwinner: h618: add Transpeed 8K618-T TV box

This is a Chinese TV box, probably very similar if not identical to
various other cheap TV boxes with the same specs:
      - Allwinner H618 SoC (4 * Arm Cortex-A53 cores, 1MB L2 cache)
      - 2 or 4GiB DDR3L DRAM
      - 32, 64, or 128 GiB eMMC flash
      - AXP313a PMIC
      - 100 Mbit/s Ethernet (using yet unsupported internal PHY)
      - HDMI port
      - 2 * USB 2.0 ports
      - microSD card slot
      - 3.5mm A/V port
      - 7-segment display
      - 5V barrel plug power supply

The PCB provides holes for soldering a UART header or cable, this is
connected to the debug UART0. UART1 is used for the Bluetooth chip,
although this isn't working yet.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20231214015312.17363-4-andre.przywara@arm.com
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>