i5400_edac: Disable device when unloading module

This was found by Huqiu Liu using a static analysis.

Reported-by: Huqiu Liu <liuhq11@mails.tsinghua.edu.cn>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Link: http://lkml.kernel.org/r/20140116162021.GY15716@redhat.com


Signed-off-by: Borislav Petkov <bp@suse.de>