[IA64] Adjust CMCI mask on CPU hotplug

Currently CMCI mask of hot-added CPU is always disabled after CPU hotplug.
We should adjust this mask depending on CMC polling state.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>