Limit the amount of texture scaling done per frame to reduce stutters

Scaling causes really bad stutters in some games on some hardware.

This should also reduce the impact of pathological cases like the first boss of FF Type-0 to be more bearable.

Causes some extra work but the heavy work gets spread over more frames. This probably will need some testing tuning before merge.

It should do nothing to speed if scaling is not enabled.
Hm yes, this is better. Should be fine to just clear the flag here I think..