avcodec/libvpxenc: Cleanup on error

This or fifo needs to be freed on errors explicitly

Fixes: memleak
Fixes: 68937/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LIBVPX_VP8_fuzzer-4830831016214528

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: James Zern <jzern@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/libvpxenc.c

@@ -2042,6 +2042,7 @@ const FFCodec ff_libvpx_vp8_encoder = {
     FF_CODEC_ENCODE_CB(vpx_encode),
     .close          = vpx_free,
     .caps_internal  = FF_CODEC_CAP_NOT_INIT_THREADSAFE |
+                      FF_CODEC_CAP_INIT_CLEANUP |
                       FF_CODEC_CAP_AUTO_THREADS,
     .p.pix_fmts     = (const enum AVPixelFormat[]){ AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVA420P, AV_PIX_FMT_NONE },
     .p.priv_class   = &class_vp8,
@@ -2118,6 +2119,7 @@ FFCodec ff_libvpx_vp9_encoder = {
     FF_CODEC_ENCODE_CB(vpx_encode),
     .close          = vpx_free,
     .caps_internal  = FF_CODEC_CAP_NOT_INIT_THREADSAFE |
+                      FF_CODEC_CAP_INIT_CLEANUP |
                       FF_CODEC_CAP_AUTO_THREADS,
     .defaults       = defaults,
     .init_static_data = vp9_init_static,