x86/motion_est: enable sad16_sse2 on k10 CPUs

The check is meant for k8 CPUs. sad16_sse2 is ~20% faster than sad16_mmxext on k10.

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
