bdinfo: Show the RAM top and approximate stack pointer

These are useful pieces of information when debugging. The RAM top shows
where U-Boot started allocating memory from, before it relocated. The
stack pointer can be checked to ensure it is in the correct region.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Nikhil M Jain <n-jain1@ti.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Nikhil M Jain <n-jain1@ti.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index fd76972..ecfd575 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -135,6 +135,14 @@
 	help
 	  Print board info
 
+config CMD_BDINFO_EXTRA
+	bool "bdinfo extra features"
+	default y if SANDBOX || X86
+	help
+	  Show additional information about the board. This uses a little more
+	  code space but provides more options, particularly those useful for
+	  bringup, development and debugging.
+
 config CMD_CONFIG
 	bool "config"
 	default SANDBOX