net/mlx5: DR: Fix cast to restricted __be32

raw_ip actual type is __be32 and not u32.
Fix that and get rid of the warning.

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_ste.c:906:31:
warning: cast to restricted __be32

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>