kbuild: remove build_unifdef target in scripts/Makefile

Since commit 2aedcd098a94 ("kbuild: suppress annoying "... is up to date."
message"), if_changed and friends nicely suppress "is up to date" messages.

We do not need per-Makefile tricks.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/Makefile b/Makefile
index f3fd2a5..6abcacf 100644
--- a/Makefile
+++ b/Makefile
@@ -1182,7 +1182,7 @@
 
 PHONY += __headers
 __headers: $(version_h) scripts_basic uapi-asm-generic archheaders archscripts
-	$(Q)$(MAKE) $(build)=scripts build_unifdef
+	$(Q)$(MAKE) $(build)=scripts scripts/unifdef
 
 PHONY += headers_install
 headers_install: __headers
diff --git a/scripts/Makefile b/scripts/Makefile
index 9d442ee..16bcb80 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -31,11 +31,6 @@
 # The following hostprogs-y programs are only build on demand
 hostprogs-y += unifdef
 
-# These targets are used internally to avoid "is up to date" messages
-PHONY += build_unifdef
-build_unifdef: $(obj)/unifdef
-	@:
-
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux