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/bf548-ezkit_defconfig b/configs/bf548-ezkit_defconfig
index 166b21a..e72dccf 100644
--- a/configs/bf548-ezkit_defconfig
+++ b/configs/bf548-ezkit_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_BF548_EZKIT=y
 CONFIG_BOOTDELAY=5
 CONFIG_SILENT_CONSOLE=y
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_SPI=y