ARM: dts: imx28-tx28: Replace deprecated spi-gpio properties

As stated in Documentation/devicetree/bindings/spi/spi-gpio.yaml,
'gpio-miso', 'gpio-mosi' and 'gpio-sck' are deprecated properties.

Use the recommeded 'miso-gpios', 'mosi-gpios' and 'sck-gpios' instead.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx28-tx28.dts

@@ -192,9 +192,9 @@ spi_gpio: spi {
 		pinctrl-names = "default";
 		pinctrl-0 = <&tx28_spi_gpio_pins>;
 
-		gpio-sck = <&gpio2 24 GPIO_ACTIVE_HIGH>;
-		gpio-mosi = <&gpio2 25 GPIO_ACTIVE_HIGH>;
-		gpio-miso = <&gpio2 26 GPIO_ACTIVE_HIGH>;
+		sck-gpios = <&gpio2 24 GPIO_ACTIVE_HIGH>;
+		mosi-gpios = <&gpio2 25 GPIO_ACTIVE_HIGH>;
+		miso-gpios = <&gpio2 26 GPIO_ACTIVE_HIGH>;
 		num-chipselects = <3>;
 		cs-gpios = <
 			&gpio2 27 GPIO_ACTIVE_LOW