also rename tud_dfu_rt_reboot_to_dfu to tud_dfu_runtime_reboot_to_dfu_cb
tested with dfu_runtime
This is really just a few descriptors and then answering to the request from the host to reboot into DFU mode. That latter part is delegated to the app since this is platform specific. Signed-off-by: Sylvain Munaut <tnt@246tNt.com>