kconfig: Fix defconfig targets

The syntax of "conf" has changed, but we never adapted
our Kconfig Makefile since we are not typically using those
targets (except for coreinfo)

Change-Id: Ib95b53d255d7456cc6d6bcc7048fcaa0db1ce142
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/10716
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
diff --git a/util/kconfig/Makefile b/util/kconfig/Makefile
index eb9e38c..ab74113 100644
--- a/util/kconfig/Makefile
+++ b/util/kconfig/Makefile
@@ -91,14 +91,14 @@
 
 defconfig: $(objk)/conf
 ifeq ($(KBUILD_DEFCONFIG),)
-	$< -d $(Kconfig)
+	$< --defconfig $(Kconfig)
 else
 	@echo "*** Default configuration is based on '$(KBUILD_DEFCONFIG)'"
-	$< -D $(KBUILD_DEFCONFIG) $(Kconfig)
+	$< --defconfig=$(KBUILD_DEFCONFIG) $(Kconfig)
 endif
 
 %_defconfig: $(objk)/conf
-	$< -D configs/$@ $(Kconfig)
+	$< --defconfig=configs/$@ $(Kconfig)
 
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