Exercise drm_mm_insert_node_in_range(), check that we only allocate from
the specified range.

v2: Use all allocation flags
v3: Don't pass in invalid ranges - these will be asserted later.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222083641.2691-13-chris@chris-wilson.co.uk