fs: return EPERM on immutable inode

In most cases, EPERM is returned on immutable inode, and there're only a
few places returning EACCES. I noticed this when running LTP on
overlayfs, setxattr03 failed due to unexpected EACCES on immutable
inode.

So converting all EACCES to EPERM on immutable inode.

Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/utimes.c b/fs/utimes.c
index 85c40f4..794f5f5 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -92,10 +92,11 @@
 		 * then we need to check permissions, because
 		 * inode_change_ok() won't do it.
 		 */
-		error = -EACCES;
+		error = -EPERM;
                 if (IS_IMMUTABLE(inode))
 			goto mnt_drop_write_and_out;
 
+		error = -EACCES;
 		if (!inode_owner_or_capable(inode)) {
 			error = inode_permission(inode, MAY_WRITE);
 			if (error)