usb_cdc: Rename usb_request_bootloader() to bootloader_request()

Rename this board API function to a more generic name.  This is in
preparation for calling the function from the canbus code.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/generic/misc.h

@@ -18,4 +18,6 @@ void *dynmem_end(void);
 
 uint16_t crc16_ccitt(uint8_t *buf, uint_fast8_t len);
 
+void bootloader_request(void);
+
 #endif // misc.h