perf ftrace: Reuse target::initial_delay

Replace perf_ftrace::initial_delay with target::initial_delay.
Specifying a negative initial_delay is meaningless for ftrace in
practice but allowed here.

Signed-off-by: Changbin Du <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Hui Wang <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-ftrace.c

···
 	/* display column headers */
 	read_tracing_file_to_stdout("trace");
 
-	if (!ftrace->initial_delay) {
+	if (!ftrace->target.initial_delay) {
 		if (write_tracing_file("tracing_on", "1") < 0) {
 			pr_err("can't enable tracing\n");
 			goto out_close_fd;
···
 
 	evlist__start_workload(ftrace->evlist);
 
-	if (ftrace->initial_delay) {
-		usleep(ftrace->initial_delay * 1000);
+	if (ftrace->target.initial_delay > 0) {
+		usleep(ftrace->target.initial_delay * 1000);
 		if (write_tracing_file("tracing_on", "1") < 0) {
 			pr_err("can't enable tracing\n");
 			goto out_close_fd;
···
 		     "Size of per cpu buffer, needs to use a B, K, M or G suffix.", parse_buffer_size),
 	OPT_BOOLEAN(0, "inherit", &ftrace.inherit,
 		    "Trace children processes"),
-	OPT_UINTEGER('D', "delay", &ftrace.initial_delay,
-		     "Number of milliseconds to wait before starting tracing after program start"),
+	OPT_INTEGER('D', "delay", &ftrace.target.initial_delay,
+		    "Number of milliseconds to wait before starting tracing after program start"),
 	OPT_PARENT(common_options),
 	};
 	const struct option latency_options[] = {

tools/perf/util/ftrace.h

···
 	int			graph_noirqs;
 	int			graph_verbose;
 	int			graph_thresh;
-	unsigned int		initial_delay;
 };
 
 struct filter_entry {