arm: dts: imx: fsl-imx8dx.dtsi: add gpio aliases to fix gpio command

The gpio command currently uses equal bank names "GPIO0_"
for all existing gpio banks, i. e.:

U-Boot# gpio status -a
Bank GPIO0_:
GPIO0_0: input: 0 [ ]
GPIO0_1: output: 1 [x] dbg1.gpios
...

Bank GPIO0_:
GPIO0_0: input: 0 [ ]
GPIO0_1: input: 0 [ ]
...

So the command is broken, it is not possible to address
a desired bank. Add gpio aliases to fix this.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
diff --git a/arch/arm/dts/fsl-imx8dx.dtsi b/arch/arm/dts/fsl-imx8dx.dtsi
index 4fc87a9..0c33eee 100644
--- a/arch/arm/dts/fsl-imx8dx.dtsi
+++ b/arch/arm/dts/fsl-imx8dx.dtsi
@@ -31,6 +31,14 @@
 		i2c1 = &i2c1;
 		i2c2 = &i2c2;
 		i2c3 = &i2c3;
+		gpio0 = &gpio0;
+		gpio1 = &gpio1;
+		gpio2 = &gpio2;
+		gpio3 = &gpio3;
+		gpio4 = &gpio4;
+		gpio5 = &gpio5;
+		gpio6 = &gpio6;
+		gpio7 = &gpio7;
 	};
 
 	memory@80000000 {