ceph: move AES iv definition to shared header

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
index c931827..a3e627f 100644
--- a/fs/ceph/crypto.c
+++ b/fs/ceph/crypto.c
@@ -75,7 +75,7 @@
 	return crypto_alloc_blkcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
 }
 
-static const u8 *aes_iv = "cephsageyudagreg";
+static const u8 *aes_iv = (u8 *)CEPH_AES_IV;
 
 static int ceph_aes_encrypt(const void *key, int key_len,
 			    void *dst, size_t *dst_len,