drm/amdgpu/display: set vblank_disable_immediate for DC

Disable vblanks immediately to save power.  I think this was
missed when we merged DC support.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1781
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_irq.c

@@ -333,7 +333,6 @@ int amdgpu_irq_init(struct amdgpu_device *adev)
 	if (!amdgpu_device_has_dc_support(adev)) {
 		if (!adev->enable_virtual_display)
 			/* Disable vblank IRQs aggressively for power-saving */
-			/* XXX: can this be enabled for DC? */
 			adev_to_drm(adev)->vblank_disable_immediate = true;
 
 		r = drm_vblank_init(adev_to_drm(adev), adev->mode_info.num_crtc);

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

@@ -1592,6 +1592,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	adev_to_drm(adev)->mode_config.cursor_width = adev->dm.dc->caps.max_cursor_size;
 	adev_to_drm(adev)->mode_config.cursor_height = adev->dm.dc->caps.max_cursor_size;
 
+	/* Disable vblank IRQs aggressively for power-saving */
+	adev_to_drm(adev)->vblank_disable_immediate = true;
+
 	if (drm_vblank_init(adev_to_drm(adev), adev->dm.display_indexes_num)) {
 		DRM_ERROR(
 		"amdgpu: failed to initialize sw for display support.\n");