panvk/csf: fix alpha-to-coverage
The equivalent bit is set correctly on JM, but was missed for CSF. Fixes dEQP-VK.pipeline.*.multisample.alpha_to_coverage*
Test run totals:
Passed: 21/588 (3.6%)
Failed: 0/588 (0.0%)
Not supported: 567/588 (96.4%)
Warnings: 0/588 (0.0%)
Waived: 0/588 (0.0%)