ice: update driver unloading field for Queue Shutdown AQ command

According to recent specification versions, the field in the Queue Shutdown
AdminQ command consisting of the "driver unloading" indication is not a 4
byte field (it is byte.bit 16.0).  Change it to a byte and remove the
unnecessary endian conversion.

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>