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/colibri_imx6_defconfig b/configs/colibri_imx6_defconfig
index f14f701..ba06a55 100644
--- a/configs/colibri_imx6_defconfig
+++ b/configs/colibri_imx6_defconfig
@@ -12,6 +12,7 @@
 CONFIG_BOOTDELAY=1
 # CONFIG_CONSOLE_MUX is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_SPL_DMA_SUPPORT=y
 CONFIG_HUSH_PARSER=y