ethtool: separate definitions that are gonna be generated

Reshuffle definitions that are gonna be generated into
ethtool_netlink_generated.h and match ynl spec order.
This should make it easier to compare the output of the ynl-gen-c
to the existing uapi header. No functional changes.

Things that are still remaining to be manually defined:
- ETHTOOL_FLAG_ALL - probably no good way to add to spec?
- some of the cable test bits (not sure whether it's possible to move to
  spec)
- some of the stats definitions (no way currently to move to spec)

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20241204155549.641348-7-sdf@fomichev.me


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