netlink: specs: nlctrl: let getfamily take a family id

ctrl_policy_family[] accepts CTRL_ATTR_FAMILY_ID and ctrl_getfamily()
looks the family up by it, but the spec lists only family-name in the
request.  C YNL generates struct members and setters from that list, so
struct nlctrl_getfamily_req has no way to carry an id and resolving a
family id - the one a client gets handed in nlmsg_type - back to a name
needs a full dump.

Python YNL happens to encode any attribute of the op's attribute set,
which is why this went unnoticed.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20260916021516.1701760-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/nlctrl.yaml

@@ -191,6 +191,7 @@ operations:
         request:
           value: 3
           attributes:
+            - family-id
             - family-name
         reply: &all-attrs
           value: 1