arm64: dts: visconti: Add device tree for TMPV7708 RM main board

Add basic support for the Visconti TMPV7708 SoC peripherals -
  - CPU
    - CA53 x 4 and 2 cluster.
    - not support PSCI, currently only spin-table is supported.
  - Interrupt controller (ARM Generic Interrupt Controller)
  - Timer (ARM architected timer)
  - UART (ARM PL011 UART controller)
  - SPI (ARM PL022 SPI controller)
  - I2C (Synopsys DesignWare APB I2C Controller)
  - Pin control (Visconti specific)

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Reviewed-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>