fftools/opt_common: replace report_and_exit() with returning an error code

Remove report_and_exit(), as it has no more users.

fftools/cmdutils.c

@@ -90,12 +90,6 @@ void register_exit(void (*cb)(int ret))
     program_exit = cb;
 }
 
-void report_and_exit(int ret)
-{
-    av_log(NULL, AV_LOG_FATAL, "%s\n", av_err2str(ret));
-    exit_program(AVUNERROR(ret));
-}
-
 void exit_program(int ret)
 {
     if (program_exit)