dix: add missing dixFreeRegistry define

[Maarten Lankhorst]

Fixes a build failure on debian's udeb builds.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
---
diff --git a/include/registry.h b/include/registry.h
index e298ab6..96be87a 100644
--- a/include/registry.h
+++ b/include/registry.h
@@ -60,6 +60,7 @@ extern _X_EXPORT void dixFreeRegistry(void);
 #define LookupResourceName(a) XREGISTRY_UNKNOWN
 
 #define dixResetRegistry() { ; }
+#define dixFreeRegistry() { ; }
 
 #endif                          /* XREGISTRY */
 #endif                          /* DIX_REGISTRY_H */