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/mx6ul_9x9_evk_defconfig b/configs/mx6ul_9x9_evk_defconfig
index 0642895..7663709 100644
--- a/configs/mx6ul_9x9_evk_defconfig
+++ b/configs/mx6ul_9x9_evk_defconfig
@@ -15,6 +15,7 @@
 CONFIG_BOOTDELAY=3
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y