ice: always return IRQ_WAKE_THREAD in ice_misc_intr()

Refactor the ice_misc_intr() function to always return IRQ_WAKE_THREAD, and
schedule the service task during the soft IRQ thread function instead of at
the end of the hard IRQ handler.

Remove the duplicate call to ice_service_task_schedule() that happened when
we got a PCI exception.

Signed-off-by: Karol Kolacinski <karol.kolacinski@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Arpana Arland <arpanax.arland@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>