Even if only `stdio_usb_serial_jtag` is enabled as STDIO, `usb_board_reset` is enabled since there should be a CDC ACM interface in any case. This is necessary, for example, to reset the board into bootloader if `stdio_cdc_acm` or `stdio_tinyusb_cdc_acm` was previously used.
The board reset function can be used on any CDC ACM interface. It is not necessary that the tinyUSB CDC ACM STDIO is used. Therefore, the board reset function is now a feature of the CDC ACM interface that don't require any other functionality.
Definition of a function as weak symbol for reset in bootloader which prints an error message if no real implementation is compiled in and
the module `riotboot_reset` is not used. This is required if the module `usb_board_reset` is used to restart the board with an application via an USB CDC ACM interface, but the board's bootloader does not support a reset in the bootloader.
The board reset function `usb_board_reset_coding_cb` can be used on any CDC ACM interface. It is not necessary that the highlevel STDIO is used. Therefore, the call of the board reset function `usb_board_reset_coding_cb` has been moved from the USBUS STDIO CDC ACM implementation to USBUS CDC ACM implementation and is thus a feature of the USBUS CDC ACM interface that don't require any other functionality.
