RAS/CEC: Check the correct variable in the debugfs error handling

Check the correct variable when handling a potential error from
debugfs_create_file(). Most likely a copy-paste botch.

[ Rewrite commit message. ]
Fixes: 011d8261 ("RAS: Add a Corrected Errors Collector")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170623062440.6726-1-christophe.jaillet@wanadoo.fr