net: usb: lan78xx: Improve error handling in EEPROM and OTP operations

Refine error handling in EEPROM and OTP read/write functions by:
- Return error values immediately upon detection.
- Avoid overwriting correct error codes with `-EIO`.
- Preserve initial error codes as they were appropriate for specific
  failures.
- Use `-ETIMEDOUT` for timeout conditions instead of `-EIO`.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241204084142.1152696-7-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>