mmc: dt: Add card-detection properties to core binding.

Required properties:

- bus-width: Number of data lines, can be <1>, <4>, or <8>

Optional properties:

Card detection:

If no property below is supplied, standard SDHCI card detect is used.

Only one of the properties in this section should be supplied:

  - broken-cd: There is no card detection available; polling must be used.

  - cd-gpios: Specify GPIOs for card detection, see gpio binding

  - non-removable: non-removable slot (like eMMC); assume always present.

Optional properties:

- wp-gpios: Specify GPIOs for write protection, see gpio binding

- cd-inverted: when present, polarity on the cd gpio line is inverted

- wp-inverted: when present, polarity on the wp gpio line is inverted

- non-removable: non-removable slot (like eMMC)

- max-frequency: maximum operating clock frequency

Example: