i40e: remove I40E_FLAG_IN_NETPOLL entirely

This flag was originally intended to be used to let some
driver code know when we were running from netpoll.
Ultimately this was not necessary and we never used it.
Let's remove it

Change-ID: I43b72483d91c1638071d2a7f389ab171ec5b796a
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>