dm: core: Show device sequence instead in dm_dump_tree()

Currently uclass index is shown in DM tree dump which ignores alias
sequence numbering. The result could be confusing since these 2 numbers
could be different. Show device sequence number instead as it's more
meaningful.

Also update documentation to use sequence number.

Signed-off-by: Zixun LI <admin@hifiphile.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/dm.rst b/doc/usage/cmd/dm.rst
index 7651507..196b22d 100644
--- a/doc/usage/cmd/dm.rst
+++ b/doc/usage/cmd/dm.rst
@@ -112,9 +112,8 @@
 uclass
     Shows the name of the uclass for the device
 
-Index
-    Shows the index number of the device, within the uclass. This shows the
-    ordering within the uclass, but not the sequence number.
+Seq
+    Shows the sequence number of the device, within the uclass.
 
 Probed
     Shows `+` if the device is active
@@ -366,7 +365,7 @@
 This example shows the abridged sandbox output::
 
     => dm tree
-    Class     Index  Probed  Driver                Name
+    Class     Seq    Probed  Driver                Name
     -----------------------------------------------------------
     root          0  [ + ]   root_driver           root_driver
     demo          0  [   ]   demo_shape_drv        |-- demo_shape_drv
diff --git a/drivers/core/dump.c b/drivers/core/dump.c
index 5ec30d5..5cbaa97 100644
--- a/drivers/core/dump.c
+++ b/drivers/core/dump.c
@@ -40,7 +40,7 @@
 	/* print the first 20 characters to not break the tree-format. */
 	printf(CONFIG_IS_ENABLED(USE_TINY_PRINTF) ? " %s  %d  [ %c ]   %s  " :
 	       " %-10.10s  %3d  [ %c ]   %-20.20s  ", dev->uclass->uc_drv->name,
-	       dev_get_uclass_index(dev, NULL),
+	       dev->seq_,
 	       flags & DM_FLAG_ACTIVATED ? '+' : ' ', dev->driver->name);
 
 	for (i = depth; i >= 0; i--) {
@@ -129,7 +129,7 @@
 {
 	struct udevice *root;
 
-	printf(" Class     Index  Probed  Driver                Name\n");
+	printf(" Class     Seq    Probed  Driver                Name\n");
 	printf("-----------------------------------------------------------\n");
 
 	root = dm_root();