review cdc-ecm enum success but comunication error

[yukelab]

1. merge usbd_cdc_ecm_start_write function to usbd_cdc_ecm_eth_tx because deduplication judge g_cdc_ecm_tx_data_length > 0 cause send data fail
2. mandatory implementation usbd_cdc_ecm_data_recv_done function to notify receive usb data to lwip
3. review CDC_ECM_DESCRIPTOR_INIT macro wMaxSegmentSize parameter error

[sakumisu]

do not remove usbd_cdc_ecm_start_write and recv_done

[sakumisu]

usbd_cdc_ecm_start_write is for eth without lwip and usbd_cdc_ecm_data_recv_done is for users to call with os.

[sakumisu]

for common, you should disable CONFIG_USBDEV_CDC_ECM_USING_LWIP, we do not use lwip for ecm. Eth rx data to usb tx and usb rx data to eth tx.

[sakumisu]

you can modify your changes in usbd_cdc_ecm_eth_rx.

[sakumisu]

1, remove g_cdc_ecm_tx_data_length = p->tot_len and change g_cdc_ecm_tx_data_length with p->tot_len in usbd_cdc_ecm_eth_tx 2, not mandatory 3, yes