Add tud_vendor_n_write_zlp_if_needed to write zlp when TX FIFO disabled.

[gogogoghost]

Describe the PR
When CFG_TUD_VENDOR_TX_BUFSIZE set to 0. User should write ZLP by themselves. But there is no way to write ZLP. This check point not supports ZLP. I think expose tu_edpt_stream_write_zlp_if_needed is a good way.

Additional context
If applicable, add any other context about the PR and/or screenshots here.

[gogogoghost]

The users can write ZLP like this:

void tud_vendor_tx_cb(uint8_t itf, uint32_t sent_bytes) { 
    // other logic...
	if(sendFinished){
		tud_vendor_write_zlp_if_needed(sent_bytes);
	}
}

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[HiFiPhile]

Thank you, could you remove extra spaces ?

[hathach]

maybe we should update the write() to allow zlp instead, let me check that option first.

[gogogoghost]

Remove this line should be OK?

tinyusb/src/tusb.c

Line 453 in 6482079

TU_VERIFY(bufsize > 0);

Will this affect other logic?

I tried this method. It works fine.

void tud_vendor_tx_cb(uint8_t itf, uint32_t sent_bytes) { 
    // other logic...
	if(sendFinished){
        if(sent_bytes&&(sent_bytes%MAX_PACKET_SIZE)==0){
            tud_vendor_write(NULL,0);
        }
	}
}

[gogogoghost]

Or we can only check buffer length when FIFO enabled.

[HiFiPhile]

Could you check https://github.com/hathach/tinyusb/tree/stream_write

[gogogoghost]

Thank you! I will test it on my board on Monday.