radv: force persample shading when required.

radv: force persample shading when required.

We need to force persample shading when
a) shader uses sample_id
b) shader uses sample_position
c) shader uses sample qualifier.

Also since ps_iter_samples can now change independently of the
rasterizer samples we need to move setting the regs more often.

This fixes:
dEQP-VK.pipeline.multisample_interpolation.centroid_interpolate_at_consistency.*
dEQP-VK.pipeline.multisample_interpolation.centroid_qualifier_inside_primitive.137_191_1.*
dEQP-VK.pipeline.multisample_interpolation.sample_interpolate_at_distinct_values.*
dEQP-VK.pipeline.multisample_interpolation.sample_qualifier_distinct_values.128_128_1.*

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>