ptp: vmclock: Set driver data before its usage

In the Linux kernel, the following vulnerability has been resolved: ptp: vmclock: Set driver data before its usage If vmclock_ptp_register() fails during probing, vmclock_remove() is called to clean up the ptp clock and misc device. It uses dev_get_drvdata() to access the vmclock state. However the driver data is not yet set at this point. Assign the driver data earlier.