[PKT_SCHED]: GRED: Dont abuse default VQ for equalizing

Introduces a new red parameter set for use in equalize mode,
although only the qavg variable and the idle period marker are
being used for now this makes it possible to allow a separate
parameter set to be used for equalize later on.

The use of this separate parameter set fixes a bogus start of
an idle period in gred_drop() which did start an idle period
on the default VQ even if equalize mode was disabled.

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