net: ethtool: pass genl_info to the ethnl parse_request operation

net: ethtool: pass genl_info to the ethnl parse_request operation

The .parse_request() ethnl operation extracts the relevant attributes
from the netlink request to populate the private req_info.

By passing genl_info as a parameter to this callback, we can use
the GENL_REQ_ATTR_CHECK() macro to check for missing mandatory
parameters.

This macro has the advantage of returning a better error explanation
through the netlink_ext_ack struct.

Convert the eeprom ethnl code to this macro, as it's the only command
yet that has mandatory request parameters.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260323095833.136266-1-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>