drm/amdgpu/virt: fix handling of the atomic flag

Use the per device drm driver feature flags rather than the
global one.  This way we can make the drm driver struct const.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201104100425.1922351-3-daniel.vetter@ffwll.ch

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

@@ -47,11 +47,13 @@ bool amdgpu_virt_mmio_blocked(struct amdgpu_device *adev)
 
 void amdgpu_virt_init_setting(struct amdgpu_device *adev)
 {
+	struct drm_device *ddev = adev_to_drm(adev);
+
 	/* enable virtual display */
 	if (adev->mode_info.num_crtc == 0)
 		adev->mode_info.num_crtc = 1;
 	adev->enable_virtual_display = true;
-	adev_to_drm(adev)->driver->driver_features &= ~DRIVER_ATOMIC;
+	ddev->driver_features &= ~DRIVER_ATOMIC;
 	adev->cg_flags = 0;
 	adev->pg_flags = 0;
 }