igb: rename igb_ptp_enable to igb_ptp_feature_enable
igb: rename igb_ptp_enable to igb_ptp_feature_enable

The name igb_ptp_enable is not synonymous with the purpose of this
function, so rename it to better explain its purpose.

Signed-off-by: Jacob Keller <952d68dd7aa4b84e9f20381084cf63d55ea3c3b1@intel.com>
Tested-by: Aaron Brown <4723df1d9a4136f7b76e1bf6434e33afc91d2139@intel.com>
Signed-off-by: Jeff Kirsher <87e35f5be20bb3e67f4ba6b86f5f6be3085b1b3a@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs