arm64: mvebu: Add Armada 3700 db-88f3720 development board support

arm64: mvebu: Add Armada 3700 db-88f3720 development board support

This patch adds basic support for the Marvell Armada 3700 DB-88F3720
development board. Supported are the following interfaces:
- UART
- SPI (incl. SPI NOR)
- I2C
- Ethernet

Signed-off-by: Stefan Roese <[email protected]>
Cc: Nadav Haklai <[email protected]>
Cc: Kostya Porotchkin <[email protected]>
Cc: Wilson Ding <[email protected]>
Cc: Victor Gu <[email protected]>
Cc: Hua Jing <[email protected]>
Cc: Terry Zhou <[email protected]>
Cc: Hanna Hawa <[email protected]>
Cc: Haim Boot <[email protected]>