Allow vendor class to be used without FIFO.

[HiFiPhile]

Describe the PR
Currently vendor class manage data the same way as CDC class.

Many protocols using buck transfer are based on packets but not data stream like CDC.
In these cases a FIFO is not needed which adds overhead, also putting all packets in FIFO adds extra difficulty to separate them since length of each packet is lost.

Additional context
I'm trying to make a CMSIS-DAP dongle.

[hathach]

we can use existing CFG_TUD_VENDOR_RX_BUFSIZE when not defined or defined to 0 mean no buffered. https://github.com/hathach/tinyusb/blob/master/examples/device/webusb_serial/src/tusb_config.h#L104-L105

I am off for TET holidays for a couple of weeks. Will try to review afterwards, thank you for your patient.

[HiFiPhile]

we can use existing CFG_TUD_VENDOR_RX_BUFSIZE when not defined or defined to 0 mean no buffered.

That's true.

Me too I was back to China for holidays:)

[hathach]

we can use existing CFG_TUD_VENDOR_RX_BUFSIZE when not defined or defined to 0 mean no buffered.

That's true.

Me too I was back to China for holidays:)

Have a great year of 🐉

[HiFiPhile]

we can use existing CFG_TUD_VENDOR_RX_BUFSIZE when not defined or defined to 0 mean no buffered.

@hathach Done

[HiFiPhile]

Additional context
I'm trying to make a CMSIS-DAP dongle.

@kkitayam Didn't see that you've already done it :)