rockchip: rk3576: Add support for ROC-RK3576-PC board

The ROC-RK3576-PC is a SBC made by Firefly, designed around the RK3576
SoC. This adds the needed board infrastructure and config for it.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
7 files changed