nvk: Clean up of multiview related code in draw and clear attachments
CTS results for dEQP-VK.multiview.*
are unchanged:
Passed: 478/505 (94.7%)
Failed: 0/505 (0.0%)
Not supported: 27/505 (5.3%)
Warnings: 0/505 (0.0%)
Waived: 0/505 (0.0%)