ice: Don't process extts if PTP is disabled

The ice_ptp_extts_event() function can race with ice_ptp_release() and
result in a NULL pointer dereference which leads to a kernel panic.

Panic occurs because the ice_ptp_extts_event() function calls
ptp_clock_event() with a NULL pointer. The ice driver has already
released the PTP clock by the time the interrupt for the next external
timestamp event occurs.

To fix this, modify the ice_ptp_extts_event() function to check the
PTP state and bail early if PTP is not ready.

Fixes: 172db5f9

 ("ice: add support for auxiliary input/output pins")
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20240702171459.2606611-3-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>