i40e: remove check for large buffer

We introduced this check in case this structure changed in the future,
the AQ definition is now mature enough that this check is no longer necessary.

Change-ID: Ic66321d0a08557dc9d8cb84029185352cb534330
Signed-off-by: Kamil Krawczyk <kamil.krawczyk@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>