i7core: Use registered memories per processor

Instead of assuming that the entire machine has either registered or
unregistered memories, do it at CPU socket based.

While here, fix a bug at i7core_mce_output_error(), where the we're
using m->cpu directly as if it would represent a socket. Instead, the
proper socket_id is given by cpu_data[m->cpu].phys_proc_id.

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