selftests/ftrace: Add fprobe related testcases

Add syntax error testcase and add-remove testcase for fprobe events.
This ensures that the fprobe events can be added/removed and parser
handles syntax errors correctly.

Link: https://lore.kernel.org/all/168507470812.913472.7489900116963294042.stgit@mhiramat.roam.corp.google.com/



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