Add missing bios_interface to api-ref for validate API

Fixing another case of bios interface missing from the api-ref
documentation, this one for the validate API.

Change-Id: I8ae3212f04a8d150af8adde5f5f87e5a5451da14

api-ref/source/baremetal-api-v1-node-management.inc

@@ -66,6 +66,7 @@ the Node's driver does not support that interface.
 
 .. rest_parameters:: parameters.yaml
 
+  - bios: v_bios
   - boot: v_boot
   - console: v_console
   - deploy: v_deploy

api-ref/source/parameters.yaml

@@ -1844,6 +1844,12 @@ uuid:
   type: string
 
 # variables returned from node-validate
+v_bios:
+  description: |
+    Status of the "bios" interface
+  in: body
+  required: true
+  type: object
 v_boot:
   description: |
     Status of the "boot" interface

releasenotes/notes/bios-interface-api-ref-validate-ddb95461adb0e478.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    The bios_interface is returned in the node validate API but it's not in the
+    api-ref documentation. This change adds it to the documentation.