drm/i915/guc: Release GuC interrupts in i915_guc_submission_disable

Like capture of GuC interrupts while enabling GuC submission, release
them while disabling GuC submission.

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1489199821-6707-1-git-send-email-sagar.a.kamble@intel.com


Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>