config: Move CONFIG_DEFAULT_FDT_FILE to defconfigs

- Add DEFAULT_FDT_FILE kconfig entry
- Move CONFIG_DEFAULT_FDT_FILE from include/configs to defconfigs

Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/common/Kconfig b/common/Kconfig
index 1198f26..6d835ca 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -203,6 +203,11 @@
 	help
 	  This options adds the board specific name to u-boot version.
 
+config DEFAULT_FDT_FILE
+	string "Default fdt file"
+	help
+	  This option is used to set the default fdt file to boot OS.
+
 config SYS_NO_FLASH
 	bool "Disable support for parallel NOR flash"
 	default n