netlink: specs: ethtool: replace underscores with dashes in names

We're trying to add a strict regexp for the name format in the spec.
Underscores will not be allowed, dashes should be used instead.
This makes no difference to C (codegen replaces special chars in names)
but gives more uniform naming in Python.

Fixes: 13e59344 ("net: ethtool: add support for symmetric-xor RSS hash")
Fixes: 46fb3ba9 ("ethtool: Add an interface for flashing transceiver modules' firmware")
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250624211002.3475021-4-kuba@kernel.org


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