It may be of interest to both compare the active HW context against the
default (aka NULL) context, to see what has been changed and if either are
corrupt.

v2: Rename the fake vma as fake.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171126220901.14735-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>