CVE-2025-68752 iavf: Implement settime64 with -EOPNOTSUPP

In the Linux kernel, the following vulnerability has been resolved: iavf: Implement settime64 with -EOPNOTSUPP ptpclocksettime assumes every ptpclock has implemented settime64. Stub it with -EOPNOTSUPP to prevent a NULL dereference. The fix is similar to commit 329d050bbe63 "gve: Implement...