thunderbolt: Move tb_xdomain_parent() to tb.h

We are going to need this for lane margining support so make it
available outside of xdomain.c.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tb.h

@@ -1132,6 +1132,11 @@ void tb_xdomain_remove(struct tb_xdomain *xd);
 struct tb_xdomain *tb_xdomain_find_by_link_depth(struct tb *tb, u8 link,
 						 u8 depth);
 
+static inline struct tb_switch *tb_xdomain_parent(struct tb_xdomain *xd)
+{
+	return tb_to_switch(xd->dev.parent);
+}
+
 int tb_retimer_scan(struct tb_port *port, bool add);
 void tb_retimer_remove_all(struct tb_port *port);
 

drivers/thunderbolt/xdomain.c

@@ -1131,11 +1131,6 @@ static int populate_properties(struct tb_xdomain *xd,
 	return 0;
 }
 
-static inline struct tb_switch *tb_xdomain_parent(struct tb_xdomain *xd)
-{
-	return tb_to_switch(xd->dev.parent);
-}
-
 static int tb_xdomain_update_link_attributes(struct tb_xdomain *xd)
 {
 	bool change = false;