drm/msm: Remove prototypes for non-existing functions

The msm_atomic_state_clear() and msm_atomic_state_free() functions are
declared but never defined. Remove their prototypes.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Patchwork: https://patchwork.freedesktop.org/patch/610618/Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_drv.h

@@ -254,8 +254,6 @@ void msm_atomic_destroy_pending_timer(struct msm_pending_timer *timer);
 void msm_atomic_commit_tail(struct drm_atomic_state *state);
 int msm_atomic_check(struct drm_device *dev, struct drm_atomic_state *state);
 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_crtc_enable_vblank(struct drm_crtc *crtc);
 void msm_crtc_disable_vblank(struct drm_crtc *crtc);