avcodec/vp9_superframe_split_bsf: Fix integer overflow in frame_size/total_size checks

Fixes: signed integer overflow: -1698586465 + -551542752 cannot be represented in type 'int'
Fixes: 4490/clusterfuzz-testcase-minimized-5210014592532480

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