nfp: devlink: add extended ack report messages

Add descriptive error messages to common devlink failures to
be more user friendly.
Signed-off-by: Ryno Swart <ryno.swart@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Link: https://lore.kernel.org/r/20231206151209.20296-3-louis.peens@corigine.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/netronome/nfp/nfp_devlink.c

@@ -75,8 +75,10 @@ nfp_devlink_port_split(struct devlink *devlink, struct devlink_port *port,
 	if (ret)
 		return ret;
 
-	if (eth_port.port_lanes % count)
+	if (eth_port.port_lanes % count) {
+		NL_SET_ERR_MSG_MOD(extack, "invalid count");
 		return -EINVAL;
+	}
 
 	/* Special case the 100G CXP -> 2x40G split */
 	lanes = eth_port.port_lanes / count;
@@ -101,8 +103,10 @@ nfp_devlink_port_unsplit(struct devlink *devlink, struct devlink_port *port,
 	if (ret)
 		return ret;
 
-	if (!eth_port.is_split)
+	if (!eth_port.is_split) {
+		NL_SET_ERR_MSG_MOD(extack, "port is not split");
 		return -EINVAL;
+	}
 
 	/* Special case the 100G CXP -> 2x40G unsplit */
 	lanes = eth_port.port_lanes;