ice: do not create xdp_frame on XDP_TX

xdp_frame is not needed for XDP_TX data path in ice driver case.
For this data path cleaning of sent descriptor will not happen anywhere
outside of the driver, which means that carrying the information about
the underlying memory model via xdp_frame will not be used. Therefore,
this conversion can be simply dropped, which would relieve CPU a bit.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>