The sum of tx bloxk eobs is needed in the machine learning based partition
early termination. The eobs are first accumulated during tx search, and
then the value associated with the best tx_size is copied to ctx for later
use.

After the sum of eobs are calculated correctly, re-enabled
ml_partition_search_early_termination speed feature.

Re-did the quality/speed test to check the impact of the fix.

1. Borg test BDRATE result:
4k set:     PSNR: +0.183%; SSIM: +0.100%;
hdres set:  PSNR: +0.168%; SSIM: +0.256%;
midres set: PSNR: +0.186%; SSIM: +0.326%;

2.Average speed gain result:
4k clips: 21%;
hd clips: 26%;
midres clips: 15%.

The result is in line with the original result.

Change-Id: I4209a95c89be03b4cbfb6a95b16885f89feddbda