drm/i915: Redo plane sanitation during readout

drm/i915: Redo plane sanitation during readout

Unify the plane disabling during state readout by pulling the code into
a new helper intel_plane_disable_noatomic(). We'll also read out the
state of all planes, so that we know which planes really need to be
diabled.

Additonally we change the plane<->pipe mapping sanitation to work by
simply disabling the offending planes instead of entire pipes. And
we do it before we otherwise sanitize the crtcs, which means we don't
have to worry about misassigned planes during crtc sanitation anymore.

v2: Reoder patches to not depend on enum old_plane_id
v3: s/for_each_pipe/for_each_intel_crtc/

Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Alex Villacís Lasso <alexvillacislasso@hotmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103223
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Thierry Reding <thierry.reding@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171117191917.11506-3-ville.syrjala@linux.intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>