board_f: Add new function to allow runtime DTB selection

Runtime U-boot dtb selection is generally a two step process. First step
is to simply use an initial generic dtb. The second step is to select
the dtb and perhaps execute additional code ones U-boot knows what board
it is running on. Embedded_dtb_select handles the second step by allowing
board specific code to run and perform what ever necessary configuration
that is needed.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/Kconfig b/common/Kconfig
index a5e3a6b..086b676 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -437,6 +437,15 @@
 
 endmenu
 
+config DTB_RESELECT
+	bool "Support swapping dtbs at a later point in boot"
+	depends on FIT_EMBED
+	help
+	  It is possible during initial boot you may need to use a generic
+	  dtb until you can fully determine the board your running on. This
+	  config allows boards to implement a function at a later point
+	  during boot to switch to the "correct" dtb.
+
 config FIT_EMBED
 	bool "Support a FIT image embedded in the U-boot image"
 	help