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/cm-bf548_defconfig b/configs/cm-bf548_defconfig
index bcf6d8f..bafce45 100644
--- a/configs/cm-bf548_defconfig
+++ b/configs/cm-bf548_defconfig
@@ -2,6 +2,7 @@
 CONFIG_TARGET_CM_BF548=y
 CONFIG_BOOTDELAY=5
 CONFIG_SILENT_CONSOLE=y
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_GPIO=y
 # CONFIG_CMD_SETEXPR is not set