zink: no handling for multisample=0 && fb_samples>1
Not exactly sure what's expected here. All samples get the same data? Only first sample gets data?
spec/ext_framebuffer_multisample/interpolation 2 centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 2 centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 2 non-centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 2 non-centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 4 centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 4 centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 4 non-centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 4 non-centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 6 centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 6 centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 6 non-centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 6 non-centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 8 centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 8 centroid-disabled: fail
spec/ext_framebuffer_multisample/interpolation 8 non-centroid-deriv-disabled: fail
spec/ext_framebuffer_multisample/interpolation 8 non-centroid-disabled: fail