platform/chrome: cros_typec_switch: Add Pin D support

The ChromeOS EC's mux interface allows us to specify whether the port
should be configured for Pin Assignment D in DisplayPort alternate mode
(i.e 2 lanes USB + 2 lanes DP). Update the function that determines mux
state to account for Pin Assignment D and return the appropriate mux
setting.

Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20230508183428.1893357-1-pmalani@chromium.org