ARM: dts: imx6ul-14x14-evk: Pass the "broken-cd" property

imx6ul-14x14-evk does not have a GPIO dedicated for reading the card
detect pin on the eSDHC2 micro-SD port.

Pass the "broken-cd" property to describe the absence of the card detect
GPIO so that polling must be used.

According to Documentation/devicetree/bindings/mmc/mmc-controller.yaml:

broken-cd:
$ref: /schemas/types.yaml#/definitions/flag
description:
There is no card detection available; polling must be used.

Even though no error is oberved in the kernel, the lack of the
'broken-cd' property caused the micro-SD to not be detected in U-Boot,
so let's improve the device tree description to make it more accurate.

Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6ul-14x14-evk.dtsi

···
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_usdhc2>;
 	no-1-8-v;
+	broken-cd;
 	keep-power-in-suspend;
 	wakeup-source;
 	status = "okay";