docs: driver-api: pti_intel_mid: Enable syntax highlighting for C code block

This makes the code snippet more readable.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/driver-api/pti_intel_mid.rst

@@ -49,7 +49,9 @@ but is not just blindly executing as 'root'. Keep in mind
 the use of ioctl(,TIOCSETD,) is not specific to the n_tracerouter
 and n_tracesink line discpline drivers but is a generic
 operation for a program to use a line discpline driver
-on a tty port other than the default n_tty::
+on a tty port other than the default n_tty:
+
+.. code-block:: c
 
   /////////// To hook up n_tracerouter and n_tracesink /////////