net: devlink: skip info_get op call if it is not defined in dumpit

In dumpit, unlike doit, the check for info_get op being defined
is missing. Add it and avoid null pointer dereference in case driver
does not define this op.

Fixes: f9cf22882c ("devlink: add device information API")
Reported-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/devlink.c

@@ -3897,6 +3897,11 @@ static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
 			continue;
 		}
 
+		if (!devlink->ops->info_get) {
+			idx++;
+			continue;
+		}
+
 		mutex_lock(&devlink->lock);
 		err = devlink_nl_info_fill(msg, devlink, DEVLINK_CMD_INFO_GET,
 					   NETLINK_CB(cb->skb).portid,