riscv: dts: canaan: fix kd233 display spi frequency

The binding for the ili9341 specifies a const spi-max-frequency of 10
MHz but the kd233 devicetree entry has it listed at 15 Mhz.
Align the devicetree with the value in the binding.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220705215213.1802496-9-mail@conchuod.ieSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/boot/dts/canaan/canaan_kd233.dts

@@ -130,7 +130,7 @@ panel@0 {
 		compatible = "ilitek,ili9341";
 		reg = <0>;
 		dc-gpios = <&gpio0 21 GPIO_ACTIVE_HIGH>;
-		spi-max-frequency = <15000000>;
+		spi-max-frequency = <10000000>;
 		status = "disabled";
 	};
 };