trace doc: add ftrace-uses.rst to doc tree

Add ftrace-uses.rst into Sphinx TOC tree. Few format issues are fixed.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2 files changed