net/mlx5e: XDP, Remove doubtful unlikely calls

It is not likely nor unlikely that the xdp buff has fragments, it
depends on the program loaded and size of the packet received.

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>