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/flea3_defconfig b/configs/flea3_defconfig
index 1dec625..fdc04a6 100644
--- a/configs/flea3_defconfig
+++ b/configs/flea3_defconfig
@@ -5,6 +5,7 @@
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=3
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="flea3 U-Boot > "
 CONFIG_CMD_SPI=y