Functions: vp9_get_pred_context_switchable_interp,
           vp9_get_pred_context_intra_inter,
           vp9_get_pred_context_single_ref_p1,
           vp9_get_pred_context_single_ref_p2.

Change-Id: I3d6fb8aee23c9062270768e1e6da416dd9bb8f96