arm64: dts: rockchip: add spi controller aliases on rk3399

There are 6 SPI controllers on RK3399 and they are all numbered in the
TRM, so let's add the appropriate aliases to the main DTSI so that any
RK3399-based board doesn't need to define the aliases themselves to
benefit from stable SPI indices in userspace.

Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Link: https://lore.kernel.org/r/20240109-rk3399-spi-aliases-v1-1-2009e44e734a@theobroma-systems.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399.dtsi

@@ -38,6 +38,12 @@ aliases {
 		serial2 = &uart2;
 		serial3 = &uart3;
 		serial4 = &uart4;
+		spi0 = &spi0;
+		spi1 = &spi1;
+		spi2 = &spi2;
+		spi3 = &spi3;
+		spi4 = &spi4;
+		spi5 = &spi5;
 	};
 
 	cpus {