kernel test robot reported htmldocs warnings:

Documentation/trace/coresight/coresight-tpda.rst:3: WARNING: Title overline too short.
Documentation/trace/coresight/coresight-tpdm.rst:3: WARNING: Title overline too short.

Extend title heading syntax (overline and underline) to match title text to
fix these warnings.

While at it, trim unneeded period in the title text.

Link: https://lore.kernel.org/linux-doc/202301210955.zYxDrLgv-lkp@intel.com/
Fixes: 758d6386 ("Documentation: trace: Add documentation for TPDM and TPDA")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230121040015.28139-2-bagasdotme@gmail.com