ixgbe: use EOPNOTSUPP instead of ENOTSUPP in ixgbe_ptp_feature_enable()

When the requested PTP feature is not supported,
ixgbe_ptp_feature_enable() returns -ENOTSUPP, causing userland programs
to get "Unknown error 524".

Since EOPNOTSUPP should be used when error is propagated to userland,
return -EOPNOTSUPP instead of -ENOTSUPP.

Fixes: 3a6a4ed ("ixgbe: Hardware Timestamping + PTP Hardware Clock (PHC)")
Signed-off-by: Kohei Enju <enjuk@amazon.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: hyperenju

drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c

@@ -641,7 +641,7 @@ static int ixgbe_ptp_feature_enable(struct ptp_clock_info *ptp,
 	 * disabled
 	 */
 	if (rq->type != PTP_CLK_REQ_PPS || !adapter->ptp_setup_sdp)
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	if (on)
 		adapter->flags2 |= IXGBE_FLAG2_PTP_PPS_ENABLED;