netlink: specs: tc: add qdisc dump to TC spec

Hook TC qdisc dump in the TC qdisc get, it only supported doit
until now and dumping will be used by the sample code.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250520161916.413298-12-kuba@kernel.org


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