netlink: specs: rt-neigh: prefix struct nfmsg members with ndm

Attach ndm- to all members of struct nfmsg. We could possibly
use name-prefix just for C, but I don't think we have any precedent
for using name-prefix on structs, and other rtnetlink sub-specs
give full names for fixed header struct members.

Fixes: bc515ed06652 ("netlink: specs: Add a spec for neighbor tables in rtnetlink")
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-9-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/rt_neigh.yaml

@@ -13,25 +13,25 @@ definitions:
     type: struct
     members:
       -
-        name: family
+        name: ndm-family
         type: u8
       -
-        name: pad
+        name: ndm-pad
         type: pad
         len: 3
       -
-        name: ifindex
+        name: ndm-ifindex
         type: s32
       -
-        name: state
+        name: ndm-state
         type: u16
         enum: nud-state
       -
-        name: flags
+        name: ndm-flags
         type: u8
         enum: ntf-flags
       -
-        name: type
+        name: ndm-type
         type: u8
         enum: rtm-type
   -