ghes_edac: Use snprintf() to silence a static checker warning

My static checker complains because the "e->location" has up to 256
characters but we are copying it into the "pvt->detail_location" which
only has space for 240 characters.  That's not counting the surrounding
text and the "e->other_detail" string which can be over 80 characters
long.

I am not familiar with this code but presumably it normally works.
Let's add a limit though for safety.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Link: http://lkml.kernel.org/r/20140801082514.GD28869@mwanda
Signed-off-by: Borislav Petkov <bp@suse.de>