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/ea20_defconfig b/configs/ea20_defconfig
index c3a4730..f24ad1a 100644
--- a/configs/ea20_defconfig
+++ b/configs/ea20_defconfig
@@ -10,6 +10,7 @@
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="ea20 > "
 # CONFIG_CMD_IMLS is not set