rasdaemon: Add support for post-processing MCA errors

rasdaemon: Add support for post-processing MCA errors

Currently, the rasdaemon performs detailed error decoding of received
MCA errors on the system only whence it is running, either as a daemon
or in the foreground.

As such, error decoding cannot be undertaken for any MCA errors received
whence the rasdaemon wasn't running. Additionally, if the error decoding
modules like edac_mce_amd too have not been loaded, error records in the
demsg buffer might correspond to raw values in associated MSRs, compelling
users to undertake decoding manually. The scenario seems more plausible on
AMD systems with Scalabale MCA (SMCA) with plans in place to remove SMCA
Extended Error Descriptions from the edac_mce_amd module in an effort to
offload SMCA Error Decoding to the rasdaemon.

As such, add support to post-process and decode MCA Errors received on AMD
SMCA systems from raw MSR values. Support for post-processing and decoding
of MCA Errors received on CPUs of other vendors can be added in the future,
as needed.

Suggested-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>