ARM: dts: aspeed-g4: Set spi-max-frequency for all flashes

Set "spi-max-frequency" to 50 MHz for all the flashes under the FMC
controller to ensure the clock frequency is calculated correctly.

Suggested-by: Cédric Le Goater <[e-mail]>
Tested-by: Jae Hyun Yoo <[e-mail]>
Signed-off-by: Tao Ren <[e-mail]>
Signed-off-by: Cédric Le Goater <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joel Stanley <[e-mail]>

arch/arm/boot/dts/aspeed-g4.dtsi

···
 				reg = < 1 >;
 				compatible = "jedec,spi-nor";
 				spi-rx-bus-width = <2>;
+				spi-max-frequency = <50000000>;
 				status = "disabled";
 			};
 			flash@2 {
 				reg = < 2 >;
 				compatible = "jedec,spi-nor";
 				spi-rx-bus-width = <2>;
+				spi-max-frequency = <50000000>;
 				status = "disabled";
 			};
 			flash@3 {
 				reg = < 3 >;
 				compatible = "jedec,spi-nor";
 				spi-rx-bus-width = <2>;
+				spi-max-frequency = <50000000>;
 				status = "disabled";
 			};
 			flash@4 {
 				reg = < 4 >;
 				compatible = "jedec,spi-nor";
 				spi-rx-bus-width = <2>;
+				spi-max-frequency = <50000000>;
 				status = "disabled";
 			};
 		};