tools: gpio: fix %llu warning in gpio-event-mon.c

Some platforms, such as mips64, don't map __u64 to long long unsigned
int so using %llu produces a warning:

gpio-event-mon.c:110:37: warning: format ‘%llu’ expects argument of type ‘long long unsigned int’, but argument 3 has type ‘__u64’ {aka ‘long unsigned int’} [-Wformat=]
110 | fprintf(stdout, "GPIO EVENT at %llu on line %d (%d|%d) ",
| ~~~^
| |
| long long unsigned int
| %lu
111 | event.timestamp_ns, event.offset, event.line_seqno,
| ~~~~~~~~~~~~~~~~~~
| |
| __u64 {aka long unsigned int}

Replace the %llu with PRIu64 and cast the argument to uint64_t.

Fixes: 03fd11b03362 ("tools/gpio/gpio-event-mon: fix warning")
Signed-off-by: Kent Gibson <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

tools/gpio/gpio-event-mon.c

···
 			ret = -EIO;
 			break;
 		}
-		fprintf(stdout, "GPIO EVENT at %llu on line %d (%d|%d) ",
-			event.timestamp_ns, event.offset, event.line_seqno,
+		fprintf(stdout, "GPIO EVENT at %" PRIu64 " on line %d (%d|%d) ",
+			(uint64_t)event.timestamp_ns, event.offset, event.line_seqno,
 			event.seqno);
 		switch (event.id) {
 		case GPIO_V2_LINE_EVENT_RISING_EDGE: