treewide: Migrate CONFIG_LAST_STAGE_INIT to Kconfig

Migrate the CONFIG_LAST_STAGE_INIT option to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/UCP1020_defconfig b/configs/UCP1020_defconfig
index 0c03372..4d88679 100644
--- a/configs/UCP1020_defconfig
+++ b/configs/UCP1020_defconfig
@@ -8,6 +8,7 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_BOARD_EARLY_INIT_R=y
+CONFIG_LAST_STAGE_INIT=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_AUTO_COMPLETE is not set
 CONFIG_SYS_PROMPT="B$ "