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/grasshopper_defconfig b/configs/grasshopper_defconfig
index 26b8a1f..784eada 100644
--- a/configs/grasshopper_defconfig
+++ b/configs/grasshopper_defconfig
@@ -1,6 +1,7 @@
 CONFIG_AVR32=y
 CONFIG_TARGET_GRASSHOPPER=y
 CONFIG_BOOTDELAY=1
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot> "
 CONFIG_AUTOBOOT_KEYED=y