kbuild: do not pass $(objtree) to scripts/mkmakefile

Since $(objtree) is always '.', it is not useful to pass it to
scripts/mkmakefile.  I assume nobody wants to run this script directly.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/Makefile b/Makefile
index 182172c..d2de86c 100644
--- a/Makefile
+++ b/Makefile
@@ -494,7 +494,7 @@
 outputmakefile:
 ifneq ($(KBUILD_SRC),)
 	$(Q)ln -fsn $(srctree) source
-	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree) $(objtree)
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree)
 endif
 
 ifeq ($(cc-name),clang)