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/bubinga_defconfig b/configs/bubinga_defconfig
index 8a72e44..fb922a8 100644
--- a/configs/bubinga_defconfig
+++ b/configs/bubinga_defconfig
@@ -6,6 +6,7 @@
 CONFIG_BOOTDELAY=5
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_VERSION_VARIABLE=y
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y