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/da850_am18xxevm_defconfig b/configs/da850_am18xxevm_defconfig
index 25fcff1..9fd9a8a 100644
--- a/configs/da850_am18xxevm_defconfig
+++ b/configs/da850_am18xxevm_defconfig
@@ -11,6 +11,7 @@
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_IMLS is not set