platform/chrome: cros_ec_typec: Update mux flags during partner removal

In cros_typec_remove_partner(), we call
cros_typec_usb_disconnect_state() which sets the switches/muxes to be in
a disconnected state. This also happens in cros_typec_configure_mux().
However, unlike there, here the mux_flags variable hasn't been updated
to reflect that a disconnection has occurred. Update the flag here
accordingly.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/chrome-platform/20220208184721.1697194-5-pmalani@chromium.org/