In order to bring consistency in-tree, migrate all subsystems code to
the new prefix <zephyr/...>. Note that the conversion has been scripted,
refer to zephyrproject-rtos#45388 for more details.
Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
Until now the whole USB device stack code is located
in the top subsys/usb directory. Move it to own directory
in preparation for upcoming extension and rework of USB support.
Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>