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/arch/powerpc/cpu/mpc86xx/Kconfig b/arch/powerpc/cpu/mpc86xx/Kconfig
index ff21c48..fcac658 100644
--- a/arch/powerpc/cpu/mpc86xx/Kconfig
+++ b/arch/powerpc/cpu/mpc86xx/Kconfig
@@ -11,10 +11,12 @@
 config TARGET_SBC8641D
 	bool "Support sbc8641d"
 	select ARCH_MPC8641
+	select BOARD_EARLY_INIT_F
 
 config TARGET_MPC8610HPCD
 	bool "Support MPC8610HPCD"
 	select ARCH_MPC8610
+	select BOARD_EARLY_INIT_F
 
 config TARGET_MPC8641HPCN
 	bool "Support MPC8641HPCN"