bootconfig: Remove unneeded CONFIG_LIBXBC

Since there is no user except CONFIG_BOOT_CONFIG and no plan
to use it from other functions, CONFIG_LIBXBC can be removed
and we can use CONFIG_BOOT_CONFIG directly.

Link: http://lkml.kernel.org/r/158098769281.939.16293492056419481105.stgit@devnote2

Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

init/Kconfig

@@ -1218,7 +1218,6 @@ endif
 config BOOT_CONFIG
 	bool "Boot config support"
 	depends on BLK_DEV_INITRD
-	select LIBXBC
 	default y
 	help
 	  Extra boot config allows system admin to pass a config file as

lib/Kconfig

@@ -566,9 +566,6 @@ config DIMLIB
 config LIBFDT
 	bool
 
-config LIBXBC
-	bool
-
 config OID_REGISTRY
 	tristate
 	help

lib/Makefile

@@ -228,7 +228,7 @@ $(foreach file, $(libfdt_files), \
 	$(eval CFLAGS_$(file) = -I $(srctree)/scripts/dtc/libfdt))
 lib-$(CONFIG_LIBFDT) += $(libfdt_files)
 
-lib-$(CONFIG_LIBXBC) += bootconfig.o
+lib-$(CONFIG_BOOT_CONFIG) += bootconfig.o
 
 obj-$(CONFIG_RBTREE_TEST) += rbtree_test.o
 obj-$(CONFIG_INTERVAL_TREE_TEST) += interval_tree_test.o