drm/i915: use compute_config in set_config v4
drm/i915: use compute_config in set_config v4

This will allow us to consult more info before deciding whether to flip
or do a full mode set.

v2:
  - don't use uninitialized or incorrect pipe masks in set_config
    failure path (Ander)
v3:
  - fixup for pipe_config changes in compute_config (Jesse)
v4:
  - drop spurious hunk in force restore path (Ander)

Signed-off-by: Jesse Barnes <bc7add126c2dbb8382bf1c28ac262b9363a32706@virtuousgeek.org>
Reviewed-by: Ander Conselvan de Oliveira <71330eafc99ba196752d2b2af84b34019e4104c2@intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs