util/kconfig: Set parameter of mkdir to only one for mingw.

The second parameter is to set file permissions for the directory, which
is not needed in mingw.

Change-Id: I88e317f075e8a39f0a280b3dd6e597d119f0f741
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/11723
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

util/kconfig/confdata.c

@@ -27,6 +27,10 @@ static int conf_lineno, conf_warnings, conf_unsaved;
 
 const char conf_defname[] = "arch/$ARCH/defconfig";
 
+#ifdef __MINGW32__
+#define mkdir(_n,_p) mkdir((_n))
+#endif
+
 static void conf_warning(const char *fmt, ...)
 {
 	va_list ap;