drm/i915: Extend non readable mcr range

Our current avoidance of non readable mcr range was not
inclusive enough. Extend the start and end.

References: HSDES#1405586840
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190809145653.2279-1-mika.kuoppala@linux.intel.com