EDAC, amd64: Don't force-enable ECC checking on newer systems

It's not recommended for the OS to try and force-enable ECC checking.
This is considered a firmware task since it includes memory training,
etc, so don't change ECC settings on Fam17h or newer systems and inform
the user.

Signed-off-by: Yazen Ghannam <Yazen.Ghannam@amd.com>
Cc: Aravind Gopalakrishnan <aravindksg.lkml@gmail.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1479850816-1595-1-git-send-email-Yazen.Ghannam@amd.com


[ Put the "forcing" message in an else branch. ]
Signed-off-by: Borislav Petkov <bp@suse.de>