mips: mt7628a.dtsi: Add SPI clock-frequency property

This patch adds the clock-frequency property to the SPI controller
DT node. It will be used by the SPI driver to calculate the baud rate.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/mips/dts/mt7628a.dtsi

@@ -76,6 +76,8 @@
 			reg = <0xb00 0x40>;
 			#address-cells = <1>;
 			#size-cells = <0>;
+
+			clock-frequency = <200000000>;
 		};
 
 		uart0: uartlite@c00 {