greybus: timesync: do not print frametime by default

Currently frametime are being printed whenever an Interface is
runtime-resumed. This is unnecessarily chatty. This patch moves the
frametime print from using pr_info() to dev_dbg().

Testing Done:
 - $ echo "module greybus +p" > /d/dynamic_debug/control

[   97.699395] greybus 1-svc: greybus frametime: ap=2042778707
1-svc=2042775185 greybus1=2042778397 1-6.6=2042778390
Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Jeffrey Carlyle <jcarlyle@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/timesync.c

@@ -746,7 +746,7 @@ static void gb_timesync_log_ping_time(struct gb_timesync_svc *timesync_svc)
 	buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 	if (buf) {
 		gb_timesync_log_frame_time(timesync_svc, buf, PAGE_SIZE);
-		pr_info("%s", buf);
+		dev_dbg(&timesync_svc->svc->dev, "%s", buf);
 		kfree(buf);
 	}
 }