drm/i915: vlv: fix switcheroo/legacy suspend/resume

During switcheroo/legacy suspend we don't call the suspend_late handler
but when resuming afterwards we call resume_early. This happened to work
so far, since suspend_late only disabled the PCI device. This changed in

commit 016970be


Author: Sagar Kamble <sagar.a.kamble@intel.com>
Date:   Wed Aug 13 23:07:06 2014 +0530

    drm/i915: Sharing platform specific sequence between runtime and system susp

after which we also saved/restored the VLV Gunit HW state in
suspend_late/resume_early. So now since we don't save the state during
suspend a following resume will restore a corrupted state.

Fix this by calling the suspend_late handler during both switcheroo and
legacy suspend.

CC: Sagar Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Sagar Kamble <sagar.a.kamble@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>