kconfig: fix build for xconfig, too

Change-Id: I1c5e3424cb56f1f10e75bb07db084c3500f3ba07
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/11768
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

util/kconfig/qconf.cc

@@ -54,6 +54,8 @@
 # define _ qgettext
 #endif
 
+int kconfig_warnings = 0;
+
 static QApplication *configApp;
 static ConfigSettings *configSettings;