freedreno/a6xx: Turn on vectorize_io

freedreno/a6xx: Turn on vectorize_io

We want this for tessellation eventually, but we can turn it on now.

Shader-db results:

total instructions in shared programs: 8612905 -> 8611387 (-0.02%)
instructions in affected programs: 164952 -> 163434 (-0.92%)

total dwords in shared programs: 11952000 -> 11950560 (-0.01%)
dwords in affected programs: 68096 -> 66656 (-2.11%)

total full in shared programs: 315019 -> 315009 (<.01%)
full in affected programs: 1642 -> 1632 (-0.61%)

total constlen in shared programs: 2463654 -> 2463654 (0.00%)
constlen in affected programs: 0 -> 0

total (ss) in shared programs: 152379 -> 152409 (0.02%)
(ss) in affected programs: 1503 -> 1533 (2.00%)

total (sy) in shared programs: 96473 -> 96525 (0.05%)
(sy) in affected programs: 654 -> 706 (7.95%)

total max_sun in shared programs: 1172454 -> 1172472 (<.01%)
max_sun in affected programs: 104 -> 122 (17.31%)

Signed-off-by: Kristian H. Kristensen <hoegsberg@google.com>
Reviewed-by: Eric Anholt <eric@anholt.net>