avformat/mov: Fix endian-dependent parsing

MOVAtom.type is always read as a little-endian number
(despite MOV/ISOBMFF being big-endian).
Fixes the matroska-dovi-write-config8 FATE-test on big-endian
arches (which runs into the "index out of range" warning message).

Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/mov.c

@@ -407,7 +407,7 @@ retry:
             atom.size -= 16;
 
             if (!key && c->found_hdlr_mdta && c->meta_keys) {
-                uint32_t index = AV_RB32(&atom.type);
+                uint32_t index = av_bswap32(atom.type); // BE number has been read as LE
                 if (index < c->meta_keys_count && index > 0) {
                     key = c->meta_keys[index];
                 } else if (atom.type != MKTAG('c', 'o', 'v', 'r')) {