v3dv: enable alphaToOne feature

This is another case of a feature that is implemented in the compiler
and that only required that we set the shader key properly from the
pipeline state, which we were already doing.

I verified we pass the tests in dEQP-VK.pipeline.multisample.alpha_to_one.*
(we only support 4x multisampling, so we can only pass a single test there),
however, the tests seem to have a bug by which they always pass, even if
the driver doesn't actually implement alpha to one correctly. I submitted
a fix to Khronos and verified that we also pass the fixed tests (and that
we failed them if we don't actually set te shader key correctly).

Reviewed-by: Alejandro PiƱeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7336>
1 file changed