mce: Panic when a core has reached a timeout

There is very little and maybe practically nothing we can do to recover
from a system where at least one core has reached a timeout during the
whole monarch cores gathering. So panic when that happens.

Link: http://lkml.kernel.org/r/20140523091041.GA21332@pd.tnic
Signed-off-by: Borislav Petkov <bp@suse.de>