net/af_xdp: make reserve/submit peek/release consistent

net/af_xdp: make reserve/submit peek/release consistent

As David pointed out, if we reserve N slots for Tx, but only submit n
slots, we would end up with an incorrect opinion of the number of available
slots later, we also would get wrong idx when we call
xsk_ring_prod__reserve next time. It also applies to
xsk_ring_cons__peek()/xsk_ring_cons__release().

This patch ensures that both reserve/submit and peek/release are
consistent.

Fixes: f1debd77efaf ("net/af_xdp: introduce AF_XDP PMD")

Suggested-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>