ubifs: Constify struct inode pointer in ubifs_crypt_is_encrypted()

...and provide a non const variant for fscrypto

Signed-off-by: Richard Weinberger <richard@nod.at>
diff --git a/fs/ubifs/crypto.c b/fs/ubifs/crypto.c
index 12a0072..25bb206 100644
--- a/fs/ubifs/crypto.c
+++ b/fs/ubifs/crypto.c
@@ -39,7 +39,7 @@
 	.flags			= FS_CFLG_INPLACE_ENCRYPTION,
 	.get_context		= ubifs_crypt_get_context,
 	.set_context		= ubifs_crypt_set_context,
-	.is_encrypted		= ubifs_crypt_is_encrypted,
+	.is_encrypted		= __ubifs_crypt_is_encrypted,
 	.empty_dir		= ubifs_crypt_empty_dir,
 	.max_namelen		= ubifs_crypt_max_namelen,
 	.key_prefix		= ubifs_key_prefix,