net: sched: gred: store red flags per virtual queue

Right now ECN marking and HARD drop (the common RED flags) can only
be configured for the entire Qdisc.  In preparation for per-vq flags
store the values in the virtual queue structure.  Setting per-vq
flags will only be allowed when no flags are set for the entire Qdisc.
For the new flags we will also make sure undefined bits are 0.

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>