The get_shared_umem function is only called when the kernel
flag XDP_UMEM_UNALIGNED_CHUNK_FLAG is defined. Move the
function implementation and associated helper so that it only
gets compiled when that flag is set.
Fixes: 74b46340e2d4 ("net/af_xdp: support shared UMEM")
Cc: stable@dpdk.org
Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>