4x4:    163 ->  123 cycles (33% faster)
8x8:    491 ->  399 cycles (23% faster)
16x16: 1889 -> 1763 cycles (7% faster)
32x32: 8311 -> 8180 cycles (1.6% faster)

Overall encoding time of first 50 frames of bus (speed 0) @ 1500kbps
goes from 1min4.33 to 1min3.00, i.e. 2.11% faster.

Change-Id: Ib52d1dbb5649b14de769d3e7a74af67440b5284f