i40e: disconnect irqs on shutdown

Combine the ICR0 shutdown with the standard interrupt shutdown, and
add the interrupt clearing to the PCI shutdown path.

This prevents the driver from allowing stray interrupts or causing
system logs from un-handled interrupts.

Change-ID: I48f6ab95cad7f8ca77c1f26c92a51cc1034ced43
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>