MIPS: Fix debugfs_create_*'s error checking method for mips/kernel/

debugfs_create_*() returns NULL on error.  Make its callers return -ENODEV
on error.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 16f8edf..4430a1f 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -601,8 +601,8 @@
 	struct dentry *d;
 
 	d = debugfs_create_dir("mips", NULL);
-	if (IS_ERR(d))
-		return PTR_ERR(d);
+	if (!d)
+		return -ENOMEM;
 	mips_debugfs_dir = d;
 	return 0;
 }