EDAC, mce_amd: Rename nb_bus_decoder to dram_ecc_decoder

EDAC, mce_amd: Rename nb_bus_decoder to dram_ecc_decoder

nb_bus_decoder() is only used for DRAM ECC errors so rename it so that
the name is more generic and descriptive.

Also, call it for DRAM ECC errors on SMCA systems.

[ Boris: rename it to real function name with a verb in it. ]

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/1479423463-8536-4-git-send-email-Yazen.Ghannam@amd.com
Signed-off-by: Borislav Petkov <bp@suse.de>