pinctrl: add kerneldoc for pinctrl_ops device tree functions

 *	group selector @pins, and the size of the array in @num_pins

 * @pin_dbg_show: optional debugfs display hook that will provide per-device

 *	info for a certain pin in debugfs

 * @dt_node_to_map: parse a device tree "pin configuration node", and create

 *	mapping table entries for it. These are returned through the @map and

 *	@num_maps output parameters. This function is optional, and may be

 *	omitted for pinctrl drivers that do not support device tree.

 * @dt_free_map: free mapping table entries created via @dt_node_to_map. The

 *	top-level @map pointer must be freed, along with any dynamically

 *	allocated members of the mapping table entries themselves. This

 *	function is optional, and may be omitted for pinctrl drivers that do

 *	not support device tree.

 */

struct pinctrl_ops {

	int (*get_groups_count) (struct pinctrl_dev *pctldev);