drm/i915/guc: Don't open log relay if GuC is not running

As we plan to continue driver load after GuC initialization
failure, we can't assume that GuC log data will be available
just because GuC was initially enabled. We must check that
GuC is still running instead.

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/20190818095204.31568-2-michal.wajdeczko@intel.com