arm64: dts: rockchip: Add on-board LED support on rk3399-ficus

Add on-board LED support for Ficus board based on the following
standard used by other 96Boards:

red:user1  default-trigger: heartbeat
red:user2  default-trigger: mmc0/disk-activity (onboard-storage)
red:user3  default-trigger: mmc1 (SD-card)
red:user4  default-trigger: none, panic-indicator
red:wlan   default-trigger: phy0tx
red:bt     default-trigger: hci0-power

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>