ethtool: eeprom: fix null-deref on genl_info in dump

The similar fix as commit 46cdedf2 ("ethtool: pse-pd: fix null-deref on
genl_info in dump") is also needed for ethtool eeprom.

Fixes: c781ff12

 ("ethtool: Allow network drivers to dump arbitrary EEPROM data")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/5575919a2efc74cd9ad64021880afc3805c54166.1666362167.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>