drm/i915: fully apply WaSkipStolenMemoryFirstPage

drm/i915: fully apply WaSkipStolenMemoryFirstPage

Don't even tell the mm allocator to handle the first page of stolen on
the affected platforms. This means that we won't inherit the FB in
case the BIOS decides to put it at the start of stolen. But the BIOS
should not be putting it at the start of stolen since it's going to
get corrupted. I suppose the bug here is that some pixels at the very
top of the screen will be corrupted, so it's not exactly easy to
notice.

We have confirmation that the first page of stolen does actually get
corrupted, so I really think we should do this in order to avoid any
possible future headaches, even if that means losing BIOS framebuffer
inheritance. Let's not use the HW in a way it's not supposed to be
used.

Notice that now ggtt->stolen_usable_size won't reflect the ending
address of the stolen usable range anymore, so we have to fix the
places that rely on this. To simplify, we'll just use U64_MAX.

v2: don't even put the first page on the mm (Chris)
v3: drm_mm_init() takes size instead of end as argument (Ville)
v4: add a comment explaining the reserved ranges (Chris)
    use 0 for start and U64_MAX for end when possible (Chris)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1481808235-27607-1-git-send-email-paulo.r.zanoni@intel.com