drm/amdgpu: Remove unused flip_flags from amdgpu_crtc

No more need since Andrey's change to use drm_crtc's version

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h

@@ -436,7 +436,6 @@ struct amdgpu_crtc {
 	enum amdgpu_interrupt_state vsync_timer_enabled;
 
 	int otg_inst;
-	uint32_t flip_flags;
 	/* After Set Mode stream will be non-NULL */
 	const struct dc_stream *stream;
 	struct drm_pending_vblank_event *event;