tools lib traceevent: Fix some comments

tools lib traceevent: Fix some comments

Update and add missing argument descriptions and fix some typo on
function comments.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Ahern <dsahern@gmail.com>
Link: http://lkml.kernel.org/r/1335157118-14658-9-git-send-email-namhyung.kim@lge.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>