kbuild: sync mixed targets handling with Linux 3.16

"make %_config all" was supported for the first time in U-Boot:
  commit 53bca5ab
  kbuild: support simultaneous board configuration and "make all"

Surprisingly it had not been working in Linux Kernel for a long time.

So I sent back the patch to the Linux Kbuild community and it was
accepted with a little code improvement, at commit 9319f453.

Now, you can do "make defconfig all" or "make %_defconfig all"
in Linux too.

This commit updates some scripts to fill the code-diff
between Linux and U-Boot.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/Makefile b/Makefile
index 38bd7a8..de65e21 100644
--- a/Makefile
+++ b/Makefile
@@ -437,12 +437,12 @@
 # We're called with mixed targets (*config and build targets).
 # Handle them one by one.
 
-PHONY += $(MAKECMDGOALS) build-one-by-one
+PHONY += $(MAKECMDGOALS) __build_one_by_one
 
-$(MAKECMDGOALS): build-one-by-one
+$(filter-out __build_one_by_one, $(MAKECMDGOALS)): __build_one_by_one
 	@:
 
-build-one-by-one:
+__build_one_by_one:
 	$(Q)set -e; \
 	for i in $(MAKECMDGOALS); do \
 		$(MAKE) -f $(srctree)/Makefile $$i; \