drm/xe: Fix NPD in ggtt_node_remove()

Make sure that ggtt_node_remove() is invoked only if both node and ggtt
are not null. Move the null checks to the caller function
xe_ggtt_node_remove().

v2: Move null check below declarations (Tejas)

Fixes: 919bb54e989c ("drm/xe: Fix missing runtime outer protection for ggtt_remove_node")
Cc: Rodrigo Vivi <[e-mail]>
Cc: Lucas De Marchi <[e-mail]>
Cc: Tejas Upadhyay <[e-mail]>
Reviewed-by: Tejas Upadhyay <[e-mail]>
Signed-off-by: Himal Prasad Ghimiray <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Rodrigo Vivi <[e-mail]>

drivers/gpu/drm/xe/xe_ggtt.c

···
 	bool bound;
 	int idx;
 
-	if (!node || !node->ggtt)
-		return;
-
 	bound = drm_dev_enter(&xe->drm, &idx);
 
 	mutex_lock(&ggtt->lock);
···
  */
 void xe_ggtt_node_remove(struct xe_ggtt_node *node, bool invalidate)
 {
-	struct xe_ggtt *ggtt = node->ggtt;
-	struct xe_device *xe = tile_to_xe(ggtt->tile);
+	struct xe_ggtt *ggtt;
+	struct xe_device *xe;
+
+	if (!node || !node->ggtt)
+		return;
+
+	ggtt = node->ggtt;
+	xe = tile_to_xe(ggtt->tile);
 
 	node->invalidate_on_remove = invalidate;