ice: ptp: don't WARN when controlling PF is unavailable

In the Linux kernel, the following vulnerability has been resolved: ice: ptp: don't WARN when controlling PF is unavailable In VFIO passthrough setups, it is possible to pass through only a PF which doesn't own the source timer. In that case the PTP controlling PF (adapter->ctrl_pf) is never initialized in the VM, so ice_get_ctrl_ptp() returns NULL and triggers WARN_ON() in ice_ptp_setup_pf(). Since this is an expected behavior in that configuration, replace WARN_ON() with an informational message and return -EOPNOTSUPP.