dt-bindings: Add Tegra SDHCI pad pdpu offset bindings

  for controllers supporting multiple voltage levels. The order of names

  should correspond to the pin configuration states in pinctrl-0 and

  pinctrl-1.

- nvidia,only-1-8-v : The presence of this property indicates that the

  controller operates at a 1.8 V fixed I/O voltage.

- nvidia,pad-autocal-pull-up-offset-3v3,

  nvidia,pad-autocal-pull-down-offset-3v3 : Specify drive strength

  calibration offsets for 3.3 V signaling modes.

- nvidia,pad-autocal-pull-up-offset-1v8,

  nvidia,pad-autocal-pull-down-offset-1v8 : Specify drive strength

  calibration offsets for 1.8 V signaling modes.

- nvidia,pad-autocal-pull-up-offset-3v3-timeout,

  nvidia,pad-autocal-pull-down-offset-3v3-timeout : Specify drive

  strength used as a fallback in case the automatic calibration times

  out on a 3.3 V signaling mode.

- nvidia,pad-autocal-pull-up-offset-1v8-timeout,

  nvidia,pad-autocal-pull-down-offset-1v8-timeout : Specify drive

  strength used as a fallback in case the automatic calibration times

  out on a 1.8 V signaling mode.

- nvidia,pad-autocal-pull-up-offset-sdr104,

  nvidia,pad-autocal-pull-down-offset-sdr104 : Specify drive strength

  calibration offsets for SDR104 mode.

- nvidia,pad-autocal-pull-up-offset-hs400,

  nvidia,pad-autocal-pull-down-offset-hs400 : Specify drive strength

  calibration offsets for HS400 mode.

  Notes on the pad calibration pull up and pulldown offset values:

    - The property values are drive codes which are programmed into the

      PD_OFFSET and PU_OFFSET sections of the

      SDHCI_TEGRA_AUTO_CAL_CONFIG register.

    - A higher value corresponds to higher drive strength. Please refer

      to the reference manual of the SoC for correct values.

    - The SDR104 and HS400 timing specific values are used in

      corresponding modes if specified.

Example:

sdhci@700b0000 {

	pinctrl-names = "sdmmc-3v3", "sdmmc-1v8";

	pinctrl-0 = <&sdmmc1_3v3>;

	pinctrl-1 = <&sdmmc1_1v8>;

	nvidia,pad-autocal-pull-up-offset-3v3 = <0x00>;

	nvidia,pad-autocal-pull-down-offset-3v3 = <0x7d>;

	nvidia,pad-autocal-pull-up-offset-1v8 = <0x7b>;

	nvidia,pad-autocal-pull-down-offset-1v8 = <0x7b>;

	status = "disabled";

};