Revert "Set up frame contexts based on frame type"

Revert "Set up frame contexts based on frame type"

This reverts commit affd9921e405063ed7815f412b15e634c8c9cfca.

Reason for revert:  Quality regression
(VP9/EndToEndTestLarge.EndtoEndPSNRTest/195 failed)

BUG=webm:1635

Original change's description:
> Set up frame contexts based on frame type
>
> In single layer ARF case, use different frame
> contexts for KF, ARF/GF, LF, OVERLAY update types.
>
> Change-Id: Iebb7f9bb430e483dea1e75fc122b9b67645ce804

Change-Id: I98a4eaa6ec0ae6616ea5ad35d1580501b7422e1b