drm/i915/selftests: Extend fault handler selftests to all memory regions

Instead of testing individually our new fault handlers, iterate over all
memory regions and test all from one interface.
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200103204137.2131004-2-chris@chris-wilson.co.uk