nfsd: use cache detail pointer from svc_export structure on cache put

Hard-coded pointer is redundant now and can be replaced.
Signed-off-by: NStanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

include/linux/nfsd/export.h

@@ -147,7 +147,7 @@ extern struct cache_detail svc_export_cache;
 
 static inline void exp_put(struct svc_export *exp)
 {
-	cache_put(&exp->h, &svc_export_cache);
+	cache_put(&exp->h, exp->cd);
 }
 
 static inline void exp_get(struct svc_export *exp)