xdp: Remove redundant warning

There is a warning in xdp_rxq_info_unreg_mem_model() when reg_state isn't
equal to REG_STATE_REGISTERED, so the warning in xdp_rxq_info_unreg() is
redundant.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/r/20211027013856.1866-1-yajun.deng@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>