Fix ixgbe flow control autoneg reporting

Fix ixgbe reporting of flow control autoneg when running under DBG 1

Reviewed by:	erj
MFC after:	2 days
Sponsored by:	Multiplay
Differential Revision:	https://reviews.freebsd.org/D5089

sys/dev/ixgbe/ixgbe_common.c

@@ -199,9 +199,12 @@ bool ixgbe_device_supports_autoneg_fc(struct ixgbe_hw *hw)
 		break;
 	}
 
-	ERROR_REPORT2(IXGBE_ERROR_UNSUPPORTED,
+	if (!supported) {
+		ERROR_REPORT2(IXGBE_ERROR_UNSUPPORTED,
 		      "Device %x does not support flow control autoneg",
 		      hw->device_id);
+	}
+
 	return supported;
 }