Check the allocation area against the known end
of address space instead of against fixed value.

v2: Return ENODEV on internal bugs (Chris)
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>