fscrypt: : Use wrapped key for metadata encryption

Importing of this commit:
https://github.com/LineageOS/android_system_vold/commit/944c48d5a4c6df1eb751b04f52c06adac35ebab6

Change-Id: I048a6c2aeff2591135f47223a99af5ddd215703c
diff --git a/crypto/fscrypt/cryptfs.h b/crypto/fscrypt/cryptfs.h
index 692d7ee..a4fe87b 100644
--- a/crypto/fscrypt/cryptfs.h
+++ b/crypto/fscrypt/cryptfs.h
@@ -200,6 +200,7 @@
 };
 
 #define DATA_MNT_POINT "/data"
+#define METADATA_MNT_POINT "/metadata"
 
 /* Return values for cryptfs_crypto_complete */
 #define CRYPTO_COMPLETE_NOT_ENCRYPTED 1