drm/amd/display: Remove unused defines

[Why]
CONFIG_DRM_AMD_DC_DCN3_0 has been folded into
CONFIG_DRM_AMD_DC_DCN and is not needed.

[How]
Drop CONFIG_DRM_AMD_DC_DCN3_0.
Signed-off-by: NQingqing Zhuo <qingqing.zhuo@amd.com>
Reviewed-by: NRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -976,12 +976,10 @@ static void event_mall_stutter(struct work_struct *work)
 	else
 		dm->active_vblank_irq_count--;
 
-#if defined(CONFIG_DRM_AMD_DC_DCN3_0)
 	dc_allow_idle_optimizations(
 		dm->dc, dm->active_vblank_irq_count == 0);
 
 	DRM_DEBUG_DRIVER("Allow idle optimizations (MALL): %d\n", dm->active_vblank_irq_count == 0);
-#endif
 
 
 	mutex_unlock(&dm->dc_lock);