ghes_edac: Register at EDAC core the BIOS report

Register GHES at EDAC MC core, in order to avoid other
drivers to also handle errors and mangle with error data.

The edac core will warrant that just one driver will be used,
so the first one to register (BIOS first) will be the one that
will be reporting the hardware errors.

For now, the EDAC driver does nothing but to register at the
EDAC core, preventing the hardware-driven mechanism to
interfere with GHES.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>