ice: Add EXTTS feature to the feature bitmap

External time stamp sources are supported only on certain devices. Enforce
the right support matrix by adding the ICE_F_PTP_EXTTS bit to the feature
bitmap set.

Co-developed-by: Maciej Machnikowski <maciej.machnikowski@intel.com>
Signed-off-by: Maciej Machnikowski <maciej.machnikowski@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Signed-off-by: Anatolii Gerasymenko <anatolii.gerasymenko@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>