Documentation: typec.rst: Use literal-block element with ascii art

Using reStructuredText literal-block element with ascii-art.
That prevents the ascii art from being processed as
reStructuredText.

Reported-by: Masanari Iida <standby24x7@gmail.com>
Reviewed-and-tested-by: Jani Nikula <jani.nikula@intel.com>
Fixes: bdecb33af34f ("usb: typec: API for controlling USB Type-C Multiplexers")
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/driver-api/usb/typec.rst

@@ -210,7 +210,7 @@ If the connector is dual-role capable, there may also be a switch for the data
 role. USB Type-C Connector Class does not supply separate API for them. The
 port drivers can use USB Role Class API with those.
 
-Illustration of the muxes behind a connector that supports an alternate mode:
+Illustration of the muxes behind a connector that supports an alternate mode::
 
                      ------------------------
                      |       Connector      |