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/mx35pdk_defconfig b/configs/mx35pdk_defconfig
index c44681f..12bdb28 100644
--- a/configs/mx35pdk_defconfig
+++ b/configs/mx35pdk_defconfig
@@ -2,6 +2,7 @@
 CONFIG_TARGET_MX35PDK=y
 CONFIG_BOOTDELAY=1
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_MMC=y