st/nine: Simplify Surface9 Managed resources implementation

st/nine: Simplify Surface9 Managed resources implementation

Remove the Surface9 code for dirty rects, used only for Managed
resources. Instead convey the information to the parent texture.

According to documentation, this seems to be the expected behaviour,
and if documentation is wrong there, that's not a problem since it can
only leads to more texture updates in corner cases.

Signed-off-by: Axel Davy <axel.davy@ens.fr>