thunderbolt: Increase path length in discovery

Currently we have only supported paths that follow daisy-chain topology
but USB4 also allows to build trees of devices. For this reason increase
maximum path length we use for discovery to be from the lowest level to
the host router and back to the same level.
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/tb.h

@@ -286,7 +286,11 @@ struct tb_path {
 
 /* HopIDs 0-7 are reserved by the Thunderbolt protocol */
 #define TB_PATH_MIN_HOPID	8
-#define TB_PATH_MAX_HOPS	7
+/*
+ * Support paths from the farthest (depth 6) router to the host and back
+ * to the same level (not necessarily to the same router).
+ */
+#define TB_PATH_MAX_HOPS	(7 * 2)
 
 /**
  * struct tb_cm_ops - Connection manager specific operations vector