examples: zephyr: certificate_rotation: fix rak5010 board file

this board file is new and missed the update from a few commits ago that
moves the board to the usb-next and new cmux symbols.

Signed-off-by: Mike Szczys <mike@golioth.io>

Author: szczys

examples/zephyr/certificate_rotation/boards/rak5010_nrf52840.conf

@@ -2,15 +2,18 @@ CONFIG_UART_ASYNC_API=y
 CONFIG_MODEM_CELLULAR_APN="internet"
 
 # USB
-CONFIG_USB_DEVICE_STACK=y
-CONFIG_USB_DEVICE_PRODUCT="RAK5010 Zephyr"
-CONFIG_USB_DEVICE_PID=0x0004
-CONFIG_USB_DEVICE_INITIALIZE_AT_BOOT=y
+CONFIG_USB_DEVICE_STACK_NEXT=y
+CONFIG_USBD_CDC_ACM_CLASS=y
+CONFIG_CDC_ACM_SERIAL_PID=0x0004
+CONFIG_CDC_ACM_SERIAL_PRODUCT_STRING="RAK5010 Zephyr"
+CONFIG_CDC_ACM_SERIAL_INITIALIZE_AT_BOOT=y
 
 CONFIG_UART_CONSOLE=y
 CONFIG_UART_LINE_CTRL=y
 CONFIG_LOG_BACKEND_RTT=n
-CONFIG_USB_CDC_ACM_LOG_LEVEL_OFF=y
+CONFIG_USBD_LOG_LEVEL_OFF=y
+CONFIG_USBD_CDC_ACM_LOG_LEVEL_OFF=y
+CONFIG_UDC_DRIVER_LOG_LEVEL_OFF=y
 
 # Networking
 CONFIG_NETWORKING=y
@@ -27,4 +30,4 @@ CONFIG_NET_SOCKETS_CONNECT_TIMEOUT=30000
 # Modem driver
 CONFIG_MODEM=y
 CONFIG_MODEM_CELLULAR=y
-CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE=1024
+CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE_EXTRA=1024