commit a481daa88fd (drm/radeon: always apply pci shutdown callbacks) breaks reboot

[Markus Trippelsdorf]

Since:

commit a481daa88fd4d6b54f25348972bba10b5f6a84d0
Author: Alex Deucher <alexander.deucher at amd.com>
Date:   Thu Sep 22 14:43:50 2016 -0400

    drm/radeon: always apply pci shutdown callbacks

    We can't properly detect all hypervisors and we
    need this to properly tear down the hardware.

I cannot reboot my machine anymore. Before reboot the monitor goes blank and
the machine stays in that state until I press the reset button.

Hardware is RS780.

-- 
Markus