v4l2_stateful_decoder: log VP8/VP9 bitstream initialization

Adds a log line when VP9 or VP9 bitstream is detected and initialized.
This is similar to what is printed for H.264.

BUG=b:227248846
TEST=tast run ${DUT} video.PlatformDecoding.v4l2_*

Change-Id: I226415ab84dad2fa0e88dc288e02f1ccf538badf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/drm-tests/+/3575413
Tested-by: Nathan Hebert <nhebert@chromium.org>
Reviewed-by: Fritz Koenig <frkoenig@chromium.org>
Commit-Queue: Nathan Hebert <nhebert@chromium.org>
diff --git a/bitstreams/bitstream_helper.c b/bitstreams/bitstream_helper.c
index f2f1175..ae0f431 100644
--- a/bitstreams/bitstream_helper.c
+++ b/bitstreams/bitstream_helper.c
@@ -48,6 +48,7 @@
 
     return true;
   } else if (init_bitstream_ivf()) {
+    LOG_INFO("Initializing VP8/VP9 bitstream");
     get_fourcc = get_fourcc_ivf;
     is_end_of_stream = is_end_of_stream_ivf;
     fill_compressed_buffer = fill_compressed_buffer_ivf;