ice: Introduce SERVICE_DIS flag and service routine functions

This patch introduces SERVICE_DIS flag to use for stopping service task.
This flag will be checked before scheduling new tasks. Also add new
functions ice_service_task_stop to stop service task.

Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>