net: usb: lan78xx: Improve error handling in WoL operations

Enhance error handling in Wake-on-LAN (WoL) operations:
- Log a warning in `lan78xx_get_wol` if `lan78xx_read_reg` fails.
- Check and handle errors from `device_set_wakeup_enable` and
  `phy_ethtool_set_wol` in `lan78xx_set_wol`.
- Ensure proper cleanup with a unified error handling path.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241216120941.1690908-7-o.rempel@pengutronix.de


Signed-off-by: Jakub Kicinski <kuba@kernel.org>