drm/via: reduce no need mutex_lock area

In function via_mem_alloc`s error branch, DRM_ERROR is protected
in the mutex_lock(&dev->struct_mutex) area.
>From the code, we see that DRM_ERROR is just an error log print
without any struct element, there is no need to protect this.
Signed-off-by: Bernard Zhao <bernard@vivo.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200814083021.8962-1-bernard@vivo.com

drivers/gpu/drm/via/via_mm.c

@@ -129,9 +129,9 @@ int via_mem_alloc(struct drm_device *dev, void *data,
 	mutex_lock(&dev->struct_mutex);
 	if (0 == ((mem->type == VIA_MEM_VIDEO) ? dev_priv->vram_initialized :
 		      dev_priv->agp_initialized)) {
+		mutex_unlock(&dev->struct_mutex);
 		DRM_ERROR
 		    ("Attempt to allocate from uninitialized memory manager.\n");
-		mutex_unlock(&dev->struct_mutex);
 		return -EINVAL;
 	}