Do the offsetting in d3d9 instead.

Notice that this also fixes vertex sampler handling in
wined3d_stateblock_apply(), since it was using the adjusted "stage" to index
the sampler_states[] array. (Coverity)
Signed-off-by: Matteo Bruni <mbruni@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>