dt-bindings: mmc: sdhci-msm: Add clk scaling dt parameters

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

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

Optional properties:

- devfreq,freq-table - specifies supported frequencies for clock scaling.

	Clock scaling logic shall toggle between these frequencies based

	on card load. In case the defined frequencies are over or below

	the supported card frequencies, they will be overridden

	during card init. In case this entry is not supplied,

	the driver will construct one based on the card

	supported max and min frequencies.

	The frequencies must be ordered from lowest to highest.

- scaling-lower-bus-speed-mode - Few hosts can support DDR52 mode at the

	same lower system voltage corner as high-speed mode. In such

	cases, it is always better to put it in DDR  mode which will

	improve the performance without any power impact.

Example:

	sdhc_1: sdhci@f9824900 {

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

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

		qcom,devfreq,freq-table = <50000000 200000000>;

		qcom,scaling-lower-bus-speed-mode = "DDR52";

	};