selftests/kprobe: Update test for no event name syntax error

The commit 208003254c32 ("selftests/kprobe: Do not test for GRP/
without event failures") removed a syntax which is no more cause
a syntax error (NO_EVENT_NAME error with GRP/).
However, there are another case (NO_EVENT_NAME error without GRP/)
which causes a same error. This adds a test for that case.

Link: https://lkml.kernel.org/r/165812790993.1377963.9762767354560397298.stgit@devnote2

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

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_syntax_errors.tc

@@ -21,6 +21,7 @@ check_error 'p:^/bar vfs_read'		# NO_GROUP_NAME
 check_error 'p:^12345678901234567890123456789012345678901234567890123456789012345/bar vfs_read'	# GROUP_TOO_LONG
 
 check_error 'p:^foo.1/bar vfs_read'	# BAD_GROUP_NAME
+check_error 'p:^ vfs_read'		# NO_EVENT_NAME
 check_error 'p:foo/^12345678901234567890123456789012345678901234567890123456789012345 vfs_read'	# EVENT_TOO_LONG
 check_error 'p:foo/^bar.1 vfs_read'	# BAD_EVENT_NAME