Convert CONFIG_BOARD_EARLY_INIT_F to Kconfig

This converts the following to Kconfig:
   CONFIG_BOARD_EARLY_INIT_F

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/devkit3250_defconfig b/configs/devkit3250_defconfig
index 2bbea13..804842e 100644
--- a/configs/devkit3250_defconfig
+++ b/configs/devkit3250_defconfig
@@ -8,6 +8,7 @@
 CONFIG_BOOTDELAY=1
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_CMD_SPI=y