extcon: usbc-tusb320: add accessory detection support

The TUSB320 can detect the following types of accessory:

  - Audio Accessory
  - Audio Accessory with charge-thru
  - Debug Accessory (DFP)
  - Debug Accessory (UFP)

Moreover, the typec subsystem can be informed of this through the
typec_set_mode() function. The information will be propagated to any
linked typec muxes. Add the necessary support to the driver.

Note that for the Debug Accessory modes, an educated guess was made that
for the USB data role, DFP implies HOST and UFP implies DEVICE. But this
might want to be made configurable at a later date.

Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>