ubifs: fix build warning after debugfs cleanup patch

Stephen writes:
	After merging the driver-core tree, today's linux-next build (arm
	multi_v7_defconfig) produced this warning:

	fs/ubifs/debug.c: In function 'dbg_debugfs_init_fs':
	fs/ubifs/debug.c:2812:6: warning: unused variable 'err' [-Wunused-variable]
	  int err, n;
	      ^~~

So fix this up properly.

Reported-by: Stephen Rothwell <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Artem Bityutskiy <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

fs/ubifs/debug.c

@@ -2821,7 +2821,7 @@ static const struct file_operations dfs_fops = {
  */
 void dbg_debugfs_init_fs(struct ubifs_info *c)
 {
-	int err, n;
+	int n;
 	const char *fname;
 	struct ubifs_debug_info *d = c->dbg;