fix(usbh_cdc/ecm): fix bulk pipe stalls for CDC-ECM on SW reboot and alt-setting switch

[siaffaf]

Problem

When using iot_usbh_ecm on ESP32-S3, two failure modes were observed:

1. Software reboot (no power cycle): After esp_restart(), the USB
   device is not power-cycled and retains its state. A failed OUT transfer
   from the previous session leaves the bulk OUT pipe in HALTED state,
   blocking all transmits permanently until a hardware power cycle.

2. IN transfer chain stops after SET_INTERFACE: The bulk IN endpoint
   does not physically exist while the data interface is in alt=0. The
   initial IN transfer fails with STATUS_ERROR, leaving the pipe HALTED.
   After SET_INTERFACE(alt=1) the endpoint becomes available but the
   receive chain never restarts.

3. Missing ZLP on bulk OUT: Ethernet frames whose size is an exact
   multiple of the 64-byte bulk MPS were not followed by a Zero Length
   Packet, causing the device to wait indefinitely for more data
   (CDC-ECM spec §3.3.1).

Fix

iot_usbh_cdc.c / iot_usbh_cdc.h

• in_xfer_cb CANCELED case: resubmit the IN transfer instead of
  dropping it. USB_TRANSFER_STATUS_CANCELED fires when the USB host
  flushes the endpoint during SET_INTERFACE — resubmitting here restarts
  the chain automatically once alt=1 is active.

• in_xfer_cb default (error) case: remove the
  _cdc_reset_transfer_endpoint + resubmit retry. Leave the pipe HALTED
  so the USB host client's internal USBH_EP_CMD_FLUSH can complete
  without hitting ESP_ERR_INVALID_STATE. The ECM layer restarts the
  transfer explicitly after SET_INTERFACE.

• usbh_cdc_restart_in_transfer() (new): clears the HALTED IN
  pipe and resubmits the IN transfer. Called by the ECM layer after
  SET_INTERFACE(alt=1) completes.

• usbh_cdc_restart_out_transfer() (new): clears the HALTED OUT
  pipe and releases the semaphore only when the pipe is actually stalled
  (semaphore count == 0). Safe to call unconditionally on both HW and
  SW reboots — no-op when the pipe is healthy.

• USB_TRANSFER_FLAG_ZERO_PACK set on the bulk OUT transfer at
  allocation time.

iot_usbh_ecm.c

Call usbh_cdc_restart_in_transfer() and usbh_cdc_restart_out_transfer()
after _ecm_config_intf() (i.e. after SET_INTERFACE(alt=1) completes).

Testing

Tested on ESP32-S3 with a USB modem (VID:1F94, PID:3002).

• Hardware reboot: ECM connects normally, no regression ✓
• Software reboot (esp_restart()): ECM now connects reliably ✓
• Frames with size that is exact multiple of 64 bytes: transmitted correctly ✓

[CLAassistant]

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