drm/i915: Introduce do_async_flip flag to intel_plane_state

There might be various logical contructs when we might want
to enable async flip, so lets calculate those and set this
flag, so that there is no need in long conditions in other
places.

v2: - Set do_async_flip flag to False, if no async flip needed.
      Lets not rely that it will be 0-initialized, but set
      explicitly, so that the logic is clear as well.

v3: - Clear do_async_flip in intel_plane_duplicate_state(Ville Syrjälä)
    - Check with do_async_flip also when calling
      intel_crtc_{enable,disable}_flip_done(Ville Syrjälä)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220124090653.14547-3-stanislav.lisovskiy@intel.com