Delete the unused irq_dynamic_disable function.

Change-ID: Ia46071066babd121c7c90f141b6210b00078de3f
Signed-off-by: NJesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: NAnjali Singhai <anjali.singhai@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>