iwlcore: support ICT interrupt

Add ICT interrupt handler support, ICT should improve CPU utilization
 since it does not require target read which is very expensive. This
 interrupt handler only added to 5000 cards and newer. Device will write
 interrupts to ICT shared table to inform driver about its interrupts.

These patches will not touch 3945 and 4965 interrupt handlers and tasklet.

Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>