Enumerating outputs before planes allows us to calculate the reference
CRC only once for each subtest instead of calculating it for each plane
tested. This removes an extra modeset during the test of each plane,
speeding up things, especially on internal panels with long power
cycle delays.

In addition when testing multiple outputs we'll now test all planes for
a given output in one go, so we can avoid the full modeset we currently
have when switching from one output to another when testing a given
plane.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>