f2fs crypto: declare some definitions for f2fs encryption feature

This definitions will be used by inode and superblock for encyption.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index d44e97f..920408a 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -91,7 +91,9 @@
 	__u8 version[VERSION_LEN];	/* the kernel version */
 	__u8 init_version[VERSION_LEN];	/* the initial kernel version */
 	__le32 feature;			/* defined features */
-	__u8 reserved[888];		/* valid reserved region */
+	__u8 encryption_level;		/* versioning level for encryption */
+	__u8 encrypt_pw_salt[16];	/* Salt used for string2key algorithm */
+	__u8 reserved[871];		/* valid reserved region */
 } __packed;
 
 /*