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/apx4devkit_defconfig b/configs/apx4devkit_defconfig
index 53d03e1..b7d7b50 100644
--- a/configs/apx4devkit_defconfig
+++ b/configs/apx4devkit_defconfig
@@ -7,6 +7,7 @@
 CONFIG_BOOTDELAY=1
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMLS is not set