vda: simplify presentation order calculation

Instead of keeping track of timestamp when added which is shaky at best
just put them at the end of the ouput queue. This should fully equal
old logic when we are always missing pts and likely be better when
pts is sporadic.
vda: replace sort time timestamp with counter

Timestamps can end up equal between two samples.
vda: increase re-order queue size to minimum 5 and based on ref frames

We must always have at least the number of reference frames to guaranteee
output in correct frame order.
vda: don't request buffer until we are sure queue depth is below limit

This avoid queue building up due to late output from decoder.