drm/i915: Move rotation from intel_plane to drm_plane_state

Runtime state that can be manipulated via properties should now go in
intel_plane_state/drm_plane_state so that it can be tracked as part of
an atomic transaction.

We add a new 'intel_create_plane_state' function so that the proper
initial value for this property (and future properties) doesn't have to
be repeated at each plane initialization site.

v2:
 - Stick rotation in common drm_plane_state rather than
   intel_plane_state. (Daniel)
 - Add intel_create_plane_state() to consolidate the places where we
   have to set initial state values.  (Ander)

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ander Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>