extcon: Add new EXTCON_CHG_USB_PD type for USB Power Delivery

extcon: Add new EXTCON_CHG_USB_PD type for USB Power Delivery

This patch adds the new EXTCON_CHG_USB_PD for USB PD (Power Delivery)[1].
The USB Power Delivery specification specifies that USB cable provides
the increased power more than 7.5W to device with larger power demand.
The EXTCON_CHG_USB_PD has the EXTCON_TYPE_CHG and EXTCON_TYPE_USB type.

[1] https://en.wikipedia.org/wiki/USB#PD

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>