i40e/i40evf: grab the AQ spinlocks before clearing registers

Make sure we have the spinlocks before we clear the ARQ and ASQ management
registers.  Also, widen the locked portion and make a sanity check earlier
in the send function to be sure we're working with safe register values.

Change-ID: I34b56044b33461ed780f3d2de8d62826cdf933f9
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>