net: sched: gred: store bytesin as a 64 bit value

32 bit counters for bytes are not really going to last long in modern
world.  Make sch_gred count bytes on a 64 bit counter.  It will still
get truncated during dump but follow up patch will add set of new
stat dump attributes.

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>