tools/seek_print: mark usage() as av_noreturn

It always calls exit(). Fixes -Wimplicit-fallthrough.

Signed-off-by: Kacper Michajłow <kasper93@gmail.com>

tools/seek_print.c

@@ -24,13 +24,14 @@
 #endif
 
 #include "libavformat/avformat.h"
+#include "libavutil/attributes.h"
 #include "libavutil/timestamp.h"
 
 #if !HAVE_GETOPT
 #include "compat/getopt.c"
 #endif
 
-static void usage(int ret)
+av_noreturn static void usage(int ret)
 {
     fprintf(ret ? stderr : stdout,
             "Usage: seek_print file [command ...]\n"