drm/i915: Exercise crossing pot boundaries in the GTT

drm/i915: Exercise crossing pot boundaries in the GTT

As the page-table trees within the GTT are naturally aligned to
power-of-two boundaries, by inserting an object that crosses a
power-of-two (and the power-of-two intervals) we can quickly check the
code for errors in switching between levels in the tree.

Signed-off-by: Chris Wilson <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]