linux-wandboard

Fix debugfs_create_file's error checking method for arch/sh/mm/

debugfs_create_file() returns NULL if an error occurs, returns -ENODEV
when debugfs is not enabled in the kernel.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>