libvpx

changed to use a fixed number for update probabity

This commit is to remove two arrays, which contain the probabilities
of how likely each probability in coef_probs table is updated. The
commit changed to use a fixed number "252".

Surprisedly, the overall impact on quality is close to zero, which
basically says the two big static arrays are not helpful at all.
derf: -0.016%, -0.020%
std-hd: 0.000%, -0.013%
yt: -0.022%, +0.007%
yt-hd: -0.038%, +0.034%

Change-Id: Ifee94d28a37dcab4f1d2b994bd5b07575be42b72