ARM: arm: colibri-imx6ull-emmc: fix emmc access

Synchronizing the device tree with linux introduced a regression.
The U-Boot specific dtsi mustn't override the alias settings for
the eMMC/SD interfaces.

Without this U-Boot cannot access the eMMC and boot the kernel.

Fixes: c21b61bff1 ("colibri-imx6ull/-emmc: synchronise device tree with linux")
Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

arch/arm/dts/imx6ull-colibri-eval-v3-u-boot.dtsi

@@ -6,7 +6,6 @@
 / {
 	aliases {
 		u-boot,dm-pre-reloc;
-		mmc0 = &usdhc1;
 		usb0 = &usbotg1; /* required for ums */
 		display0 = &lcdif;
 	};