i40evf: Drop packet split receive routine

As part of preparation for the rx-refactor, remove the
packet split receive routine and ancillary code.

Some of the split related context set up code stays in
i40e_virtchnl_pf.c in case an older VF driver tries to load
and still wants to use packet split.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>