docs: thunderbolt: Allow creating cross-references for ABI

Now that Documentation/ABI is processed by automarkup, let it
generate cross-references for the corresponding ABI file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/a655e770e1446f91088f579b79ae890a19771119.1739254867.git.mchehab+huawei@kernel.org

Author: mchehab

Documentation/admin-guide/thunderbolt.rst

@@ -28,7 +28,7 @@ should be a userspace tool that handles all the low-level details, keeps
 a database of the authorized devices and prompts users for new connections.
 
 More details about the sysfs interface for Thunderbolt devices can be
-found in ``Documentation/ABI/testing/sysfs-bus-thunderbolt``.
+found in Documentation/ABI/testing/sysfs-bus-thunderbolt.
 
 Those users who just want to connect any device without any sort of
 manual work can add following line to