add simple echo cdc serial demo add cdc device send/receive API refractor descriptor refractor cdc.h add usbd driver function - init - bus_reset
refractor keyboard dev demo app
- SCSI_CMD_MODE_SELECT_6 - SCSI_CMD_MODE_SENSE_6 - SCSI_CMD_PREVENT_ALLOW_MEDIUM_REMOVAL fix msc device bug with no data unsupported command complete msc device demo with ram disk of 8KB