ARM: dts: imx6qdl-sabre: Add mmc aliases

If not specified, the mmc0 and mmc1 devices will be the devices
mmc@2190000 and mmc@2194000, which are in disabled state on the iMX.6
Sabrelite devices.

The actual SD card reader devices are the ones at mmc@2198000 and
mmc@219c000.

Set aliases to use the correct mmc devices order.
Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-sabrelite.dtsi

@@ -14,6 +14,11 @@ chosen {
 		stdout-path = &uart2;
 	};
 
+	aliases {
+		mmc0 = &usdhc3;
+		mmc1 = &usdhc4;
+	};
+
 	memory@10000000 {
 		device_type = "memory";
 		reg = <0x10000000 0x40000000>;