netlink: specs: correct the spec of ethtool

The spec for Ethtool is a bit inaccurate. We don't currently
support dump. Context is only accepted as input and not echoed
to output (which is a separate bug).

Fixes: a353318ebf ("tools: ynl: populate most of the ethtool spec")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20240724234249.2621109-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/ethtool.yaml

@@ -1753,15 +1753,14 @@ operations:
         request:
           attributes:
             - header
+            - context
         reply:
           attributes:
             - header
-            - context
             - hfunc
             - indir
             - hkey
             - input_xfrm
-      dump: *rss-get-op
     -
       name: plca-get-cfg
       doc: Get PLCA params.