ceph: clean up header guards

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/crush/hash.h b/fs/ceph/crush/hash.h
index ff48e110..91e8842 100644
--- a/fs/ceph/crush/hash.h
+++ b/fs/ceph/crush/hash.h
@@ -1,5 +1,5 @@
-#ifndef _CRUSH_HASH_H
-#define _CRUSH_HASH_H
+#ifndef CEPH_CRUSH_HASH_H
+#define CEPH_CRUSH_HASH_H
 
 #define CRUSH_HASH_RJENKINS1   0