anv/i965: enable GCM but not GVN yet
More tweaking is needed before we can enable GVN but GCM is ready:
Shader-db results (SKL):
total instructions in shared programs: 14947192 -> 14947048 (<.01%)
instructions in affected programs: 6138 -> 5994 (-2.35%)
helped: 12
HURT: 0
total cycles in shared programs: 324868402 -> 324755126 (-0.03%)
cycles in affected programs: 303795 -> 190519 (-37.29%)
helped: 15
HURT: 0
Edited by Jordan Justen