drm/msm: subclass drm_atomic_state

This will give the kms backends a slot to stash their own hw specific
global state.

Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_drv.h

@@ -179,6 +179,9 @@ int msm_atomic_check(struct drm_device *dev,
 		     struct drm_atomic_state *state);
 int msm_atomic_commit(struct drm_device *dev,
 		struct drm_atomic_state *state, bool nonblock);
+struct drm_atomic_state *msm_atomic_state_alloc(struct drm_device *dev);
+void msm_atomic_state_clear(struct drm_atomic_state *state);
+void msm_atomic_state_free(struct drm_atomic_state *state);
 
 int msm_register_address_space(struct drm_device *dev,
 		struct msm_gem_address_space *aspace);