net/mlx5e: TC, Fix memory leak with rules with internal port

Fix a memory leak with decap rule with internal port as destination
device. The driver allocates a modify hdr action but doesn't set
the flow attr modify hdr action which results in skipping releasing
the modify hdr action when releasing the flow.

backtrace:
    [<000000005f8c651c>] krealloc+0x83/0xd0
    [<000000009f59b143>] alloc_mod_hdr_actions+0x156/0x310 [mlx5_core]
    [<000000002257f342>] mlx5e_tc_match_to_reg_set_and_get_id+0x12a/0x360 [mlx5_core]
    [<00000000b44ea75a>] mlx5e_tc_add_fdb_flow+0x962/0x1470 [mlx5_core]
    [<0000000003e384a0>] __mlx5e_add_fdb_flow+0x54c/0xb90 [mlx5_core]
    [<00000000ed8b22b6>] mlx5e_configure_flower+0xe45/0x4af0 [mlx5_core]
    [<00000000024f4ab5>] mlx5e_rep_indr_offload.isra.0+0xfe/0x1b0 [mlx5_core]
    [<000000006c3bb494>] mlx5e_rep_indr_setup_tc_cb+0x90/0x130 [mlx5_core]
    [<00000000d3dac2ea>] tc_setup_cb_add+0x1d2/0x420

Fixes: b16eb3c8

 ("net/mlx5: Support internal port as decap route device")
Signed-off-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>