gma500: display displaced vertically by a few lines

[Holger Schurig]

Okay, I've can now circle the problem out. What did I do:

* I used vanilla-3.9.2 kernel, but brougth drivers/gpu/drm/gma500 to
the state of Linus' git tree commit id
0cdbee3e811b1bbb347c61814c8570658f2ab15c. This was shortly after
gma500 moved out of staging
* then I did "git format-patch
0cdbee3e811b1bbb347c61814c8570658f2ab15c..master
drivers/gpu/drm/gma500/"
* I then took the following patches to get this antique gma500 driver
compile against kernel 3.9.2 with it's updated DRM:
** psb/0001-drm-gma500-fix-compile-error.patch
** psb/0002-drm-move-the-fb-bpp-depth-helper-into-the-core.patch
** psb/0020-drm-Replace-pitch-with-pitches-in-drm_framebuffer.patch
** psb/0095-gma500-remove-the-second-argument-of-k-un-map_atomic.patch
** psb/0151-drm-Make-the-.mode_fixup-operations-mode-argument-a-.patch
(modified)
** psb/0152-drm-kill-reclaim_buffers-callback.patch
** psb/0175-mm-kill-vma-flag-VM_RESERVED-and-mm-reserved_vm-coun.patch
** psb/0178-drm-gma500-drm_connector_property-drm_object_propert.patch
(modified)

Now this franken-gma500_gfx driver runs perfectly with
xserver-xorg-video-fbdev and doesn't have the displaced vertical
screen issue.

Now I can roll in other patches until I find the culprit.