Remove MEM_TYPE_ZERO_COPY in favor of the new MEM_TYPE_XSK_BUFF_POOL
APIs.

v4->v5: Fixed "warning: Excess function parameter 'alloc' description
        in 'ice_alloc_rx_bufs_zc'" and "warning: Excess function
        parameter 'xdp' description in
        'ice_construct_skb_zc'". (Jakub)
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: intel-wired-lan@lists.osuosl.org
Link: https://lore.kernel.org/bpf/20200520192103.355233-10-bjorn.topel@gmail.com