net/mlx5e: Use same coding pattern for Rx and Tx flows

Remove intermediate variable in favor of having similar coding style
for Rx and Tx add rule functions.

Reviewed-by: Raed Salem <raeds@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>