adding v4l2 example code

v4l2/t.c

@@ -16,7 +16,9 @@ int		verbosity;
 void help(int k)
 {
 puts("Options :");
+puts("\t-d\tselect the video device");
 puts("\t-K\tset the K parameter");
+puts("\t-l\tlist video devices");
 puts("\t-v\tincrease verbosity");
 exit(0);
 }