Unify the high bit-depth forward hybrid transforms

The SSE2 version high bit-depth forward hybrid transforms are
essentially using the C functions via cross referencing to 1-D
functions in vp9_dct.c. This commit unifies the two versions and
removes the unnecessary dependency.

Change-Id: Ib4d0702a138f8daf7d0bd97c141ee7088f293765
4 files changed