drm/i915/guc: Replace check for golden context size

In the other places in this function, guc->ads_map is being protected
from access when it's not yet set. However the last check is actually
about guc->ads_golden_ctxt_size been set before.  These checks should
always match as the size is initialized on the first call to
guc_prep_golden_context(), but it's clearer if we have a single return
and check for guc->ads_golden_ctxt_size.

This is just a readability improvement, no change in behavior.

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220216174147.3073235-12-lucas.demarchi@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c

@@ -500,10 +500,10 @@ static int guc_prep_golden_context(struct intel_guc *guc)
 		addr_ggtt += alloc_size;
 	}
 
-	if (iosys_map_is_null(&guc->ads_map))
-		return total_size;
+	/* Make sure current size matches what we calculated previously */
+	if (guc->ads_golden_ctxt_size)
+		GEM_BUG_ON(guc->ads_golden_ctxt_size != total_size);
 
-	GEM_BUG_ON(guc->ads_golden_ctxt_size != total_size);
 	return total_size;
 }