fs: encode_fh: return FILEID_INVALID if invalid fid_type

This patch is a follow up on below patch:

[PATCH] exportfs: add FILEID_INVALID to indicate invalid fid_type
commit: 216b6cbdcbd86b1db0754d58886b466ae31f5a63

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Acked-by: Sage Weil <sage@inktank.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
index a836118..c585bc6 100644
--- a/fs/xfs/xfs_export.c
+++ b/fs/xfs/xfs_export.c
@@ -48,7 +48,7 @@
 	case FILEID_INO32_GEN_PARENT | XFS_FILEID_TYPE_64FLAG:
 		return 6;
 	}
-	return 255; /* invalid */
+	return FILEID_INVALID;
 }
 
 STATIC int
@@ -90,7 +90,7 @@
 	len = xfs_fileid_length(fileid_type);
 	if (*max_len < len) {
 		*max_len = len;
-		return 255;
+		return FILEID_INVALID;
 	}
 	*max_len = len;