extcon: add Realtek DHC RTD SoC Type-C driver

This patch adds the extcon driver for Realtek DHC (digital home center)
RTD SoCs type-c module. This can be used to detect whether the port is
configured as a downstream or upstream facing port. And notify the status
of extcon to listeners.

Link: https://lore.kernel.org/lkml/20230904051253.23208-2-stanley_chang@realtek.com/


Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>