net/mlx5e: TC ipv4 tunnel encap offload cosmetic changes

Move around some settings of variables as pre-step to make things
more robust and clear for the ipv6 case in down-stream patch.
This patch doesn't change any functionality.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>