lav*,tests: remove several register_all calls

avdevice_register_all() is still required to register devices into
lavf (this is required due to lavd being somewhat of a hack).

Signed-off-by: Josh de Kock <josh@itanimul.li>

tools/ismindex.c

@@ -791,8 +791,6 @@ int main(int argc, char **argv)
     int split = 0, ismf = 0, i;
     struct Tracks tracks = { 0, .video_track = -1, .audio_track = -1 };
 
-    av_register_all();
-
     for (i = 1; i < argc; i++) {
         if (!strcmp(argv[i], "-n")) {
             basename = argv[i + 1];