Add Calix ONU Vendor ID (#344)

* Add Calix ONU Vendor ID

Source: 
http://web.archive.org/web/20240604184845/https://i.ebayimg.com/images/g/N1UAAOSwM~RlVTjO/s-l1600.jpg 

(look at FSAN marking on the label)

Confirmed from Uboot logs.

* Sort Calix Vendor ID

Author: milankragujevic

_gpon/vendor.md

@@ -19,6 +19,7 @@ Here is a list of the most popular Vendor IDs:
 | `ASKY` | `41534b59` | Askey                |
 | `CDKT` | `43444B54` | KingType             |
 | `CIGG` | `43494747` | Cig                  |
+| `CXNK` | `43584e4b` | Calix                |
 | `DDKT` | `44444b54` | DKT                  |
 | `DLNK` | `444c4e4b` | Dlink                |
 | `DSNW` | `44534e57` | DASAN                |