drm: Allow drivers to modify plane_state in prepare_fb/cleanup_fb

The drivers have to modify the atomic plane state during the prepare_fb
callback so they track allocations, reservations and dependencies for
this atomic operation involving this fb. In particular, how else do we
set the plane->fence from the framebuffer!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818180017.20508-1-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index c29a429..b37b8ef 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1225,9 +1225,9 @@
 void intel_finish_page_flip_mmio(struct drm_i915_private *dev_priv, int pipe);
 void intel_check_page_flip(struct drm_i915_private *dev_priv, int pipe);
 int intel_prepare_plane_fb(struct drm_plane *plane,
-			   const struct drm_plane_state *new_state);
+			   struct drm_plane_state *new_state);
 void intel_cleanup_plane_fb(struct drm_plane *plane,
-			    const struct drm_plane_state *old_state);
+			    struct drm_plane_state *old_state);
 int intel_plane_atomic_get_property(struct drm_plane *plane,
 				    const struct drm_plane_state *state,
 				    struct drm_property *property,