net/mlx5e: Move sample attr allocation to tc_action sample parse op

There is no reason to wait with the kmalloc to after parsing all
other actions. There could still be a failure later and before
offloading the rule. So alloc the mem when parsing.
The memory is being released on mlx5e_flow_put() which is called
also on error flow.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Oz Shlomo <ozsh@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>