[nrf noup] zephyr: Disable Thingy:53 board specific USB CDC config

MCUBoot configures USB CDC by its own. There is no need for
BOARD_SERIAL_BACKEND_CDC_ACM option to configure anything which is
later overwritten anyway.

Jira: NCSDK-18596

Signed-off-by: Mateusz Kapala <mateusz.kapala@nordicsemi.no>

boot/zephyr/boards/thingy53_nrf5340_cpuapp.conf

@@ -34,6 +34,7 @@ CONFIG_NORDIC_QSPI_NOR_STACK_WRITE_BUFFER_SIZE=16
 CONFIG_MULTITHREADING=y
 
 # USB
+CONFIG_BOARD_SERIAL_BACKEND_CDC_ACM=n
 CONFIG_USB_DEVICE_REMOTE_WAKEUP=n
 CONFIG_USB_DEVICE_MANUFACTURER="Nordic Semiconductor ASA"
 CONFIG_USB_DEVICE_PRODUCT="Bootloader Thingy:53"