arm64: mvebu: Add support for the Marvell Armada 3700 SoC

arm64: mvebu: Add support for the Marvell Armada 3700 SoC

The Armada 3700 integrates the following interfaces (not complete list):
- Dual Cortex-A53 ARMv8
- USB 3.0
- SATA 3.0
- PCIe 2.0
- 2 x Gigabit Ethernet 1Gbps / 2.5Gbps
- ...

This patch adds basic support for this ARMv8 based SoC into U-Boot.
Future patches will integrate other device drivers and board support
for the Marvell DB-88F3720 development board.

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]>