arm: add initial support for the Phytium Durian Board

This adds platform code and the device tree for the Phytium Durian Board.
The initial support comprises the UART and the PCIE.

Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Kever Yang <kever.yang@rock-chips.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>

Signed-off-by: Steven Hao <liuhao@phytium.com.cn>