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/sbc8548_defconfig b/configs/sbc8548_defconfig
index fe2a6b9..cac78e7 100644
--- a/configs/sbc8548_defconfig
+++ b/configs/sbc8548_defconfig
@@ -6,6 +6,7 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_BOOTDELAY=10
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_I2C=y
 # CONFIG_CMD_SETEXPR is not set