added xiao nrf54l15 support for otbr

Kconfig

@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2023 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+# Set product string for USB device
+config CDC_ACM_SERIAL_PRODUCT_STRING
+	default "Thread Co-Processor"
+	depends on USB_DEVICE_STACK_NEXT
+
+menu "Zephyr Kernel"
+source "Kconfig.zephyr"
+endmenu
+
+module = OT_COPROCESSOR
+module-str = ot_coprocessor
+source "$(ZEPHYR_BASE)/subsys/logging/Kconfig.template.log_config"
+
+config RCP_SAMPLE_HCI
+	bool "Bluetooth HCI USB support for the coprocessor sample"
+	select EXPERIMENTAL