to read some random system memory address
with some iommu this will broke the crtc engine and will lead to
broken display and iommu error message.

So to avoid this, disable crtc. For flicker less boot we will need
to avoid moving the vram start address.

This patch should also fix :

https://bugs.freedesktop.org/show_bug.cgi?id=42373

Cc: <stable@vger.kernel.org>
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
hñoS–