Change 2 motion search counts to be tile data

Change 2 motion search counts to be tile data

This patch modified the motion search counts used in:
https://chromium-review.googlesource.com/#/c/305640/

These 2 counts were originally added as thread data, and used to
make decisions in motion search. The tile encoding order can be
inconsistent while using different number of threads, which can
cause bitstream mismatch. Here moved them to tile data to solve
the issue.

BUG=webm:1322

Change-Id: Iedc4477aef1746aa0a4f84d88a1156296fd3ba87