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/mvebu_db-88f3720_defconfig b/configs/mvebu_db-88f3720_defconfig
index 7f4569d..8b5229c 100644
--- a/configs/mvebu_db-88f3720_defconfig
+++ b/configs/mvebu_db-88f3720_defconfig
@@ -10,6 +10,7 @@
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_ARCH_EARLY_INIT_R=y
+CONFIG_BOARD_EARLY_INIT_F=y
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_SF=y