net/mlx5: fix match MPLS over GRE with key

Currently PMD needs previous layer information in order to set
corresponding match field for MPLSoGRE or MPLSoUDP.

GRE_KEY item is missing as supported previous layer when translate
item MPLS, which causes flow[1] cannot match MPLS over GRE traffic.

According to RFC4023, MPLS over GRE tunnel with optional key
field needs to be supported too.

By adding missing GRE_KEY as supported previous layer fix problem.

[1]:
flow create 0 ingress pattern eth / ipv6 / gre k_bit is 1 / gre_key /
mpls label is 966138 / end actions queue index 1 / mark id 0xa / end

Fixes: a7a0365 ("net/mlx5: match GRE key and present bits")
Cc: stable@dpdk.org

Signed-off-by: Xiaoyu Min <jackmin@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>

drivers/net/mlx5/mlx5_flow_dv.c

@@ -9064,6 +9064,8 @@ flow_dv_translate_item_mpls(void *matcher, void *key,
 			 MLX5_UDP_PORT_MPLS);
 		break;
 	case MLX5_FLOW_LAYER_GRE:
+		/* Fall-through. */
+	case MLX5_FLOW_LAYER_GRE_KEY:
 		MLX5_SET(fte_match_set_misc, misc_m, gre_protocol, 0xffff);
 		MLX5_SET(fte_match_set_misc, misc_v, gre_protocol,
 			 RTE_ETHER_TYPE_MPLS);