Previously the transform type sets used for 16x32/32x16 transform
sizes corresponded to 16x16 transforms. Now they correspond to
32x32 transforms with a reduced available set.

BDRATE impact:
0.05% worse for lowres, 0.13% worse for midres

Change-Id: I01d405d497c13837f5404f9e0caf8c571f3b26cf