net/mlx5e: RX, Remove doubtful unlikely call

When building an skb in non-linear mode, it is not likely nor unlikely
that the xdp buff has fragments, it depends on the size of the packet
received.

Signed-off-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>