drm_atomic_helper_damage_iter_init() + drm_atomic_for_each_plane_damage()
returns the full plane area in case no damaged area was set by
userspace or it was discarted by driver.

This is important to fix the rendering of userspace applications that
does frontbuffer rendering and notify driver about dirty areas but do
not set any dirty clips.

With this we don't need to worry about to check and mark the whole
area as damaged in page flips.

Another important change here is the move of
drm_atomic_add_affected_planes() call, it needs to called late
otherwise the area of all the planes would be added to pipe_clip and
not saving power.

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914212507.177511-4-jose.souza@intel.com