We don't need these functions anymore. The only one which was actually
used is vp9_add_constant_residual_32x32. Addition of
vp9_short_idct32x32_1_add eliminates this single usage. SSE2 optimized
version of vp9_short_idct32x32_1_add will be added in the next patch set,
right now it is only C implementation. Now we have all idct functions
implemented in a consistent manner.

Change-Id: I63df79a13cf62aa2c9360a7a26933c100f9ebda3