net: sched: gred: provide a better structured dump and expose stats

Currently all GRED's virtual queue data is dumped in a single
array in a single attribute.  This makes it pretty much impossible
to add new fields.  In order to expose more detailed stats add a
new set of attributes.  We can now expose the 64 bit value of bytesin
and all the mark stats which were not part of the original design.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>