EDAC, mce_amd: Don't report poison bit on Fam15h, bank 4

MCA_STATUS[43] has been defined as "Poison" or "Reserved" for every bank
since Fam15h except for Fam15h, bank 4 in which case it's defined as
part of the McaStatSubCache bitfield.

Filter out that case.

Reported-by: Dean Liberty <Dean.Liberty@amd.com>
Signed-off-by: Yazen Ghannam <Yazen.Ghannam@amd.com>
Cc: Aravind Gopalakrishnan <aravindksg.lkml@gmail.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/1479478222-19896-1-git-send-email-Yazen.Ghannam@amd.com


[ Split an almost unparseable ternary conditional, add a comment. ]
Signed-off-by: Borislav Petkov <bp@suse.de>