We should not call edac_mc_del_mc() if a corresponding call to
edac_mc_add_mc() has not been performed yet.

So here, we should go to err instead of err2 to branch at the right
place of the error handling path.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20180107205400.14068-1-christophe.jaillet@wanadoo.frSigned-off-by: Borislav Petkov <bp@suse.de>