sh: j2: Drop incorrect SPI controller spi-max-frequency property

The J2 SPI controller bindings never allowed spi-max-frequency property
in the controller node.  Neither old spi-bus.txt bindings, nor new DT
schema allows it.  Linux driver does not parse that property from
controller node, thus drop it from DTS as incorrect hardware
description.  The SPI child device has already the same property with
the same value, so functionality should not be affected.

Cc: Kousik Sanagavarapu <five231003@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Tested-by: Rob Landley <rob@landley.net>
Link: https://lore.kernel.org/r/20240322064221.25776-1-krzysztof.kozlowski@linaro.orgSigned-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

arch/sh/boot/dts/j2_mimas_v2.dts

@@ -71,8 +71,6 @@ spi0: spi@40 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 
-			spi-max-frequency = <25000000>;
-
 			reg = <0x40 0x8>;
 
 			sdcard@0 {