zink: pass nr_cbufs to vkCmdSetColorWriteEnableEXT

VUID-vkCmdDrawMultiEXT-attachmentCount-06667 specifies that
attachmentCount needs to match the attachment count from the
blend-state, but we're setting it to maxColorAttachments.
90 jobs for !17884 with zink-color-write-fix in 16 minutes and 15 seconds (queued for 8 seconds)
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