drm/i915/uc: Cleanup fw fetch only if it was successful

We can rely on firmware status AVAILABLE to determine if any
firmware cleanup is required. Also don't unconditionally reset
fw status to SELECTED as we will loose MISSING/ERROR codes.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
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/20190817131144.26884-2-michal.wajdeczko@intel.com