selftests/ftrace: Add test case for synthetic event syntax errors

Add a selftest that verifies that the syntax error messages and caret
positions are correct for most of the possible synthetic event syntax
error cases.

Link: https://lkml.kernel.org/r/af611928ce79f86eaf0af8654f1d7802d5cc21ff.1602598160.git.zanussi@kernel.org



Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>