gve: merge xdp and xsk registration

gve: merge xdp and xsk registration

The existence of both of these xdp_rxq and xsk_rxq is redundant. xdp_rxq
can be used in both the zero-copy mode and the copy mode case. XSK pool
memory model registration is prioritized over normal memory model
registration to ensure that memory model registration happens only once
per queue.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
Signed-off-by: Jeroen de Borst <jeroendb@google.com>
Link: https://patch.msgid.link/20250717152839.973004-3-jeroendb@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>