arm64: dts: rockchip: remove max-freq from &spi1 node for Hugsun X99

A test with the command below does not detect all errors
in combination with 'additionalProperties: false' and
allOf:
  - $ref: "spi-controller.yaml#"

'additionalProperties' applies to all properties that are not
accounted-for by 'properties' or 'patternProperties' in
the immediate schema.

First when we combine spi-rockchip.yaml and
spi-controller.yaml it gives this error:

arch/arm64/boot/dts/rockchip/rk3399-hugsun-x99.dt.yaml: spi@ff1d0000:
'max-freq' does not match any of the regexes:
'^.*@[0-9a-f]+$', '^slave$'

'max-freq' is not a valid property name for spi nodes,
so remove it.

make ARCH=arm64 dtbs_check
DT_SCHEMA_FILES=Documentation/devicetree/bindings/spi/spi-rockchip.yaml

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200309125145.14455-1-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-hugsun-x99.dts

@@ -610,7 +610,6 @@ &spdif {
 
 &spi1 {
 	status = "okay";
-	max-freq = <10000000>;
 
 	flash@0 {
 		compatible = "jedec,spi-nor";