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/zc5601_defconfig b/configs/zc5601_defconfig
index 4e7385e..d48fcf1 100644
--- a/configs/zc5601_defconfig
+++ b/configs/zc5601_defconfig
@@ -16,6 +16,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg,MX6Q"
 CONFIG_BOOTDELAY=3
 CONFIG_DEFAULT_FDT_FILE="imx6q-zc5601.dtb"
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_SF=y