selftests/ftrace: Add tracepoint probe test case

Add test cases for tracepoint probe events.

Link: https://lore.kernel.org/all/168507477214.913472.11218388626709005588.stgit@mhiramat.roam.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>