Documentation: coresight: tpdm: Add dummy comment after sysfs list

kernel test robot reported htmldocs warning:

Documentation/trace/coresight/coresight-tpdm.rst:43: WARNING: Document may not end with a transition.

Since there is no more documentation left for TPDM, fix the warning by adding
dummy comment, thus creating the required text transition.

Link: https://lore.kernel.org/linux-doc/202301210955.zYxDrLgv-lkp@intel.com/
Fixes: 758d6386 ("Documentation: trace: Add documentation for TPDM and TPDA")
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NBagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230121040015.28139-3-bagasdotme@gmail.com

Documentation/trace/coresight/coresight-tpdm.rst

@@ -41,3 +41,5 @@ Root: ``/sys/bus/coresight/devices/tpdm<N>``
     value -  1 or 2.
 
 ----
+
+.. This text is intentionally added to make Sphinx happy.