doc(virtio-mem): document PATCH API in swagger and docs

Add entry for the patch API in Swagger and in the docs.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

docs/device-api.md

@@ -104,6 +104,7 @@ specification:
 | `MemoryHotplugConfig`     | total_size_mib     |    O     |       O        |      O       |        O         |     O      |      O       |     O      |   **R**    |
 |                           | slot_size_mib      |    O     |       O        |      O       |        O         |     O      |      O       |     O      |   **R**    |
 |                           | block_size_mi      |    O     |       O        |      O       |        O         |     O      |      O       |     O      |   **R**    |
+| `MemoryHotplugSizeUpdate` | requested_size_mib |    O     |       O        |      O       |        O         |     O      |      O       |     O      |   **R**    |
 
 \* `Drive`'s `drive_id`, `is_root_device` and `partuuid` can be configured by
 either virtio-block or vhost-user-block devices.

src/firecracker/swagger/firecracker.yaml

@@ -549,6 +549,26 @@ paths:
           description: Internal server error
           schema:
             $ref: "#/definitions/Error"
+    patch:
+      summary: Updates the size of the hotpluggable memory region
+      operationId: patchMemoryHotplug
+      description:
+        Updates the size of the hotpluggable memory region. The guest will plug and unplug memory to
+        hit the requested memory.
+      parameters:
+        - name: body
+          in: body
+          description: Hotpluggable memory size update
+          required: true
+          schema:
+            $ref: "#/definitions/MemoryHotplugSizeUpdate"
+      responses:
+        204:
+          description: Hotpluggable memory configured
+        default:
+          description: Internal server error
+          schema:
+            $ref: "#/definitions/Error"
     get:
       summary: Retrieves the status of the hotpluggable memory
       operationId: getMemoryHotplug
@@ -1422,6 +1442,15 @@ definitions:
         description: (Logical) Block size for the hotpluggable memory in MiB. This will determine the logical
           granularity of hot-plug memory for the guest. Refer to the device documentation on how to tune this value.
 
+  MemoryHotplugSizeUpdate:
+    type: object
+    description:
+      An update to the size of the hotpluggable memory region.
+    properties:
+      requested_size_mib:
+        type: integer
+        description: New target region size.
+
   MemoryHotplugStatus:
     type: object
     description: