drm/i915/uc: Explicitly sanitize GuC/HuC on failure and finish

Explicitly sanitize GuC/HuC on load failure and when we finish
using them to make sure our fw state tracking is always correct.

While around, use new helper in uc_reset_prepare.

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>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190522193203.23932-6-michal.wajdeczko@intel.com