net: ethtool: call .parse_request for SET handlers

In preparation for using req_info to carry parameters between SET
and NTF - call .parse_request during ethnl_default_set_doit().

The main question here is whether .parse_request is intended to be
GET-specific. Originally the SET handling was delegated to each subcommand
directly - ethnl_default_set_doit() and .set callbacks in ethnl_request_ops
did not exist. Looking at existing users does not shed much light, all
of the following subcommands use .parse_request but have no SET handler
(and no NTF):

  net/ethtool/eeprom.c
  net/ethtool/rss.c
  net/ethtool/stats.c
  net/ethtool/strset.c
  net/ethtool/tsinfo.c

There's only one which does have a SET:

  net/ethtool/pause.c

where .parse_request handling is used to select which statistics to query.
Not relevant for SET but also harmless.

Going back to RSS (which doesn't have SET today) .parse_request parses
the rss_context ID. Using the req_info struct to pass the context ID
from SET to NTF will be very useful.

Switch to ethnl_default_parse(), effectively adding the .parse_request
for SET handlers.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Tested-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20250623231720.3124717-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/ethtool/netlink.c

@@ -878,9 +878,7 @@ static int ethnl_default_set_doit(struct sk_buff *skb, struct genl_info *info)
 	if (!req_info)
 		return -ENOMEM;
 
-	ret = ethnl_parse_header_dev_get(req_info, info->attrs[ops->hdr_attr],
-					 genl_info_net(info), info->extack,
-					 true);
+	ret = ethnl_default_parse(req_info, info,  ops, true);
 	if (ret < 0)
 		goto out_free_req;