dt-bindings: mmc: Add information for DLL register properties

	"cal"	- reference clock for RCLK delay calibration (optional)

	"sleep"	- sleep clock for RCLK delay calibration (optional)

- qcom,ddr-config: Certain chipsets and platforms require particular settings

	for the DDR_CONFIG register. Use this field to specify the register

	value as per the Hardware Programming Guide.

- qcom,dll-config: Chipset and Platform specific value. Use this field to

	specify the DLL_CONFIG register value as per Hardware Programming Guide.

Example:

	sdhc_1: sdhci@f9824900 {

		clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>;

		clock-names = "core", "iface";

		qcom,dll-config = <0x000f642c>;

		qcom,ddr-config = <0x80040868>;

	};

	sdhc_2: sdhci@f98a4900 {

		clocks = <&gcc GCC_SDCC2_APPS_CLK>, <&gcc GCC_SDCC2_AHB_CLK>;

		clock-names = "core", "iface";

		qcom,dll-config = <0x0007642c>;

		qcom,ddr-config = <0x80040868>;

	};