arm64: dts: rockchip: Enable SPI1 on Ficus

Enable SPI1 exposed on both Low and High speed expansion connectors
of Ficus. SPI1 has 3 different chip selects wired as below:

CS0 - Serial Flash (unpopulated)
CS1 - Low Speed expansion
CS2 - High Speed expansion

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