arm64: dts: rockchip: add rk356x gmac1 node

Add the gmac1 controller to the rk356x device tree.
This is the controller common to both the rk3568 and rk3566.

Signed-off-by: Peter Geis <pgwipeout@gmail.com>
Link: https://lore.kernel.org/r/20210728180034.717953-5-pgwipeout@gmail.com


[adjusted sorting a bit]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>