Add a trigger for IO-MCA errors

mcelog socket triggers currently only trigger on memory
(and possibly yellow bit) errors.

This patch enables mcelog to trigger a custom action on
the Bus and Interconnect errors, including IO MCA.

[AK: Minor cleanups. Fix warnings.]
Signed-off-by: Rui Wang <rui.y.wang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Fix incorrect asprintf in yellow.c

Signed-off-by: Andi Kleen <ak@linux.intel.com>