Correct data size estimation for odd size video

Given the largest transform size is 32x32, this commmit changes size
estiiation based on the size rounding up to 32 multiples to avoid
insufficient buffer allocations.

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=36

Change-Id: I6eab09dc6acdc0f5a6bcadb918d62c4852aae21f
1 file changed