ice: check whether PTP is initialized in ice_ptp_release()

PTP is currently only supported on E810 devices, it is checked
in ice_ptp_init(). However, there is no check in ice_ptp_release().
For other E800 series devices, ice_ptp_release() will be wrongly executed.

Fix the following calltrace.

  INFO: trying to register non-static key.
  The code is fine but needs lockdep annotation, or maybe
  you didn't initialize this object before use?
  turning off the locking correctness validator.
  Workqueue: ice ice_service_task [ice]
  Call Trace:
   dump_stack_lvl+0x5b/0x82
   dump_stack+0x10/0x12
   register_lock_class+0x495/0x4a0
   ? find_held_lock+0x3c/0xb0
   __lock_acquire+0x71/0x1830
   lock_acquire+0x1e6/0x330
   ? ice_ptp_release+0x3c/0x1e0 [ice]
   ? _raw_spin_lock+0x19/0x70
   ? ice_ptp_release+0x3c/0x1e0 [ice]
   _raw_spin_lock+0x38/0x70
   ? ice_ptp_release+0x3c/0x1e0 [ice]
   ice_ptp_release+0x3c/0x1e0 [ice]
   ice_prepare_for_reset+0xcb/0xe0 [ice]
   ice_do_reset+0x38/0x110 [ice]
   ice_service_task+0x138/0xf10 [ice]
   ? __this_cpu_preempt_check+0x13/0x20
   process_one_work+0x26a/0x650
   worker_thread+0x3f/0x3b0
   ? __kthread_parkme+0x51/0xb0
   ? process_one_work+0x650/0x650
   kthread+0x161/0x190
   ? set_kthread_struct+0x40/0x40
   ret_from_fork+0x1f/0x30

Fixes: 4dd0d5c3 ("ice: add lock around Tx timestamp tracker flush")
Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>