Kconfig: Add EXPERT option

For similar reasons to why the Linux Kernel has an EXPERT option, we too
want an option to allow for tweaking of some options that while normally
should remain hidden, may need to be changed in some cases.

Signed-off-by: Tom Rini <trini@ti.com>
Acked-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Kconfig

@@ -58,6 +58,14 @@ config CC_OPTIMIZE_FOR_SIZE
 
 endmenu		# General setup
 
+menuconfig EXPERT
+        bool "Configure standard U-Boot features (expert users)"
+        help
+          This option allows certain base U-Boot options and settings
+          to be disabled or tweaked. This is for specialized
+          environments which can tolerate a "non-standard" U-Boot.
+          Only use this if you really know what you are doing.
+
 menu "Boot images"
 
 config SPL_BUILD