adding Synology FS6400 (#3053)

* adding Synology FS6400

* Update FS6400.yaml

---------

Co-authored-by: Marco Dieckhoff <marco.dieckhoff@gmail.com>
Co-authored-by: Harry <Harry@cadby.co.uk>

device-types/Synology/FS6400.yaml

@@ -0,0 +1,36 @@
+---
+manufacturer: Synology
+model: FS6400
+slug: synology-fs6400
+part_number: FS6400
+u_height: 2
+is_full_depth: true
+weight: 14.5
+weight_unit: kg
+airflow: front-to-rear
+comments: '[Synology FS6400 Datasheet](https://global.synologydownload.com/download/Document/Hardware/DataSheet/FlashStation/20-year/FS6400/enu/Synology_FS6400_Data_Sheet_enu.pdf)'
+front_image: true
+rear_image: true
+module-bays:
+  - name: PSU-1
+    label: '1'
+    position: PSU-1
+  - name: PSU-2
+    label: '2'
+    position: PSU-2
+  - name: PCIe Slot 1
+    position: '1'
+  - name: PCIe Slot 2
+    position: '2'
+interfaces:
+  - name: LAN1
+    type: 1000base-t
+  - name: LAN2
+    type: 1000base-t
+  - name: LAN3
+    type: 10gbase-t
+  - name: LAN4
+    type: 10gbase-t
+console-ports:
+  - name: Console
+    type: de-9