Small valgrind suppression tweak for statically linked ffmpeg

Small valgrind suppression tweak for statically linked ffmpeg

BUG=441333
The stack is slightly different now that we're statically linking.

{
   Memcheck:Uninitialized
   fun:av_packet_unpack_dictionary
   fun:add_metadata_from_side_data
   fun:avcodec_decode_video2
   fun:avcodec_decode_video2  <=== THIS REPEATED LINE IS GONE NOW
   fun:_ZN5media18FFmpegVideoDecoder12FFmpegDecodeERK13scoped_refptrINS_13DecoderBufferEEPb
...

}

Example log:
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%283%29/builds/46166/steps/memory%20test%3A%20media/logs/202EB30501710F5D

Committed: https://crrev.com/5c06be0db44b0b6dc01d272e37d798218659b7c0
Cr-Commit-Position: refs/heads/master@{#333610}

[chcunningham, 2015-06-09 22:44:00]

chcunningham@chromium.org changed reviewers:
+ dalecurtis@chromium.org, thestig@chromium.org

[Lei Zhang, 2015-06-09 22:53:27]

lgtm

[chcunningham, 2015-06-09 22:59:48]

The CQ bit was checked by chcunningham@chromium.org

[commit-bot: I haz the power, 2015-06-09 23:03:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1173813002/1

[commit-bot: I haz the power, 2015-06-09 23:48:04]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-09 23:49:06]

Patchset 1 (id:??) landed as
https://crrev.com/5c06be0db44b0b6dc01d272e37d798218659b7c0
Cr-Commit-Position: refs/heads/master@{#333610}