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/stv0991_defconfig b/configs/stv0991_defconfig
index f808ce2..9973021 100644
--- a/configs/stv0991_defconfig
+++ b/configs/stv0991_defconfig
@@ -7,6 +7,7 @@
 CONFIG_BOOTDELAY=3
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SYS_PROMPT="STV0991> "
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Hit SPACE in %d seconds to stop autoboot.\n"