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/configs/mx25pdk_defconfig b/configs/mx25pdk_defconfig
index b4afb05..c3ab7c2 100644
--- a/configs/mx25pdk_defconfig
+++ b/configs/mx25pdk_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_TARGET_MX25PDK=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/mx25pdk/imximage.cfg"
+CONFIG_DEFAULT_FDT_FILE="imx25-pdk.dtb"
 CONFIG_BOOTDELAY=1
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y