doc: announce queue stats moving to xstats

doc: announce queue stats moving to xstats

Queue stats will be removed from basic stats to xstats.

It will be PMDs responsibility to fill queue stats based on number of
queues they have.

Until all PMDs implement the xstats, a temporary
'RTE_ETH_DEV_AUTOFILL_QUEUE_XSTATS' device flag created. PMDs switched
to the xstats should clear this flag to bypass the ethdev layer autofill
for queue stats.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>