drm/i915/guc: skip disabling CTBs before sanitizing the GuC

If we're about to sanitize the GuC, something might have going wrong
beforehand, so we should avoid trying to talk to it. Even if GuC is
still running fine, the sanitize will reset its internal state and clear
the CTB registration, so there is still no need to explicitly do so.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/2469


Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210603051630.2635-2-matthew.brost@intel.com