drm/i915/guc: Make sure to sanitize CT status

drm/i915/guc: Make sure to sanitize CT status

We are sanitizing firmware status and old mmio message, but
we forget to sanitize CT status.

Fixes: e0068b0f5445 ("drm/i915/guc: Introduce guc_is_ready")
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200207131938.2787828-1-chris@chris-wilson.co.uk
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>