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/ls1021aiot_qspi_defconfig b/configs/ls1021aiot_qspi_defconfig
index be39889..d57c853 100644
--- a/configs/ls1021aiot_qspi_defconfig
+++ b/configs/ls1021aiot_qspi_defconfig
@@ -2,6 +2,7 @@
 CONFIG_TARGET_LS1021AIOT=y
 CONFIG_DEFAULT_DEVICE_TREE="ls1021a-iot-duart"
 CONFIG_SYS_EXTRA_OPTIONS="QSPI_BOOT"
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_OF_CONTROL=y
 CONFIG_DM=y
 CONFIG_SPI_FLASH=y