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/pm9261_defconfig b/configs/pm9261_defconfig
index 6bc5f6f..332e5dd 100644
--- a/configs/pm9261_defconfig
+++ b/configs/pm9261_defconfig
@@ -7,6 +7,7 @@
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SYS_PROMPT="pm9261> "
 # CONFIG_CMD_BDI is not set
 # CONFIG_CMD_IMI is not set