[PKT_SCHED]: GRED: Cleanup dumping

Avoids the allocation of a buffer by appending the VQs directly
to the skb and simplifies the code by using the appropriate
message construction macros.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>