ice: fix driver unload flow

As part of the driver unload flow, a PF reset is issued which may still
cause an interrupt to be generated by the device.  Do not clear the
interrupt scheme until the reset is complete and there are no pending
transactions otherwise a hardware error may occur.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>