linux-phytec-ti

arm64: dts: rockchip: Add rk3368 mailbox device nodes

This adds mailbox device nodes in dts.

Mailbox is used by the Rockchip CPU cores to communicate
requests to MCU processor.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>