net/mlx5: Fix fw reporter diagnose output

Restore fw reporter diagnose to print the syndrome even if it is zero.
Following the cited commit, in this case (syndrome == 0) command returns no
output at all.

This fix restores command output in case syndrome is cleared:
$ devlink health diagnose pci/0000:82:00.0 reporter fw
    Syndrome: 0

Fixes: d17f98bf ("net/mlx5: devlink health: use retained error fmsg API")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/health.c

@@ -452,10 +452,10 @@ mlx5_fw_reporter_diagnose(struct devlink_health_reporter *reporter,
 	struct health_buffer __iomem *h = health->health;
 	u8 synd = ioread8(&h->synd);
 
+	devlink_fmsg_u8_pair_put(fmsg, "Syndrome", synd);
 	if (!synd)
 		return 0;
 
-	devlink_fmsg_u8_pair_put(fmsg, "Syndrome", synd);
 	devlink_fmsg_string_pair_put(fmsg, "Description", hsynd_str(synd));
 
 	return 0;