drm/xe/configfs: Fix documentation warning

Fix this warning while building the documentation:

	Documentation/gpu/xe/xe_configfs:9: drivers/gpu/drm/xe/xe_configfs.c:138:
	WARNING: Definition list ends without a blank line; unexpected unindent.

That also makes it better formatted in the output.

While at it, also fix the underline length in "Overview".

Fixes: e2b33fce5e ("drm/xe/configfs: Improve documentation steps")
Reviewed-by: Raag Jadav <raag.jadav@intel.com>
Link: https://lore.kernel.org/r/20250911-wa-bb-cmds-v4-2-c8f7e48f7eae@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_configfs.c

@@ -21,7 +21,7 @@
  * DOC: Xe Configfs
  *
  * Overview
- * =========
+ * ========
  *
  * Configfs is a filesystem-based manager of kernel objects. XE KMD registers a
  * configfs subsystem called ``xe`` that creates a directory in the mounted
@@ -34,7 +34,7 @@
  *
  * To create a device, the ``xe`` module should already be loaded, but some
  * attributes can only be set before binding the device. It can be accomplished
- * by blocking the driver autoprobe:
+ * by blocking the driver autoprobe::
  *
  *	# echo 0 > /sys/bus/pci/drivers_autoprobe
  *	# modprobe xe