netlink: specs: nfsd: 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, if used, replaces special
chars in names) but it gives more uniform naming in Python.

Fixes: 13727f85b4 ("NFSD: introduce netlink stubs")
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20250624211002.3475021-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/nfsd.yaml

@@ -27,7 +27,7 @@ attribute-sets:
         name: proc
         type: u32
       -
-        name: service_time
+        name: service-time
         type: s64
       -
         name: pad
@@ -139,7 +139,7 @@ operations:
             - prog
             - version
             - proc
-            - service_time
+            - service-time
             - saddr4
             - daddr4
             - saddr6