can: esd_usb: Rework display of error messages

can: esd_usb: Rework display of error messages

- esd_usb_open(): Get rid of duplicate "couldn't start device: %d\n"
  message already printed from esd_usb_start().
- Fix duplicate printout of network device name when network device
  is registered. Add an unregister message for the network device
  as counterpart to the register message.
- Add the printout of error codes together with the error messages
  in esd_usb_close() and some in esd_usb_probe(). The additional error
  codes should lead to a better understanding what is really going
  wrong.
- Convert all occurrences of error status prints to use "ERR_PTR(err)"
  instead of printing the decimal value of "err".
- Rename retval to err in esd_usb_read_bulk_callback() to make the
  naming of error status variables consistent with all other functions.

Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>
Link: https://patch.msgid.link/20250821143422.3567029-5-stefan.maetje@esd.eu
[mkl: minor change patch description to imperative language]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>