drm/i915/guc: Do not wait for firmware load atomically

It does not look like this code needs to wait atomically?

Higher in the call chain it calls the GEM API and I do
not see that the section is under any spin locks or such.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Alex Dai <yu.dai@intel.com>
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>