ARM: dts: stm32: argon: remove spidev node

Commit 956b200a ("spi: spidev: Warn loudly if instantiated from DT
as "spidev"") states that there should not be spidev nodes in DTs.
Remove this non-HW description. There won't be a regression because it
won't bind since 2015 anyhow.

Fixes: 16e3e44c ("ARM: dts: stm32: Add support for the emtrion emSBC-Argon")
Cc: Reinhold Mueller <reinhold.mueller@emtrion.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm/boot/dts/stm32mp157c-emstamp-argon.dtsi

@@ -435,12 +435,6 @@ &spi1 {
 	pinctrl-0 = <&spi1_pins_a>;
 	cs-gpios = <&gpioz 3 0>;
 	status = "disabled";
-
-	spidev@0  {
-		compatible = "spidev";
-		reg = <0>;
-		spi-max-frequency = <100000>;
-	};
 };
 
 &timers1 {