net/mlx5: Refactor imm_inval_pkey field in cqe struct

The imm_inval_pkey field can hold four different types of data,
depends on the usage, the data could be one of the below:
- Immediate field of the received message
- Invalidate rkey
- Pkey of the packet
- Flow table metadata

Current implementation doesn't reflect the intended usage of the
field at usage time.

Reflect the different types by replace this field with a union,
modify code where this field is used to reflect its intended
usage.

Signed-off-by: Raed Salem <raeds@mellanox.com>
Reviewed-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

include/linux/mlx5/device.h

@@ -767,7 +767,12 @@ struct mlx5_cqe64 {
 	u8		l4_l3_hdr_type;
 	__be16		vlan_info;
 	__be32		srqn; /* [31:24]: lro_num_seg, [23:0]: srqn */
-	__be32		imm_inval_pkey;
+	union {
+		__be32 immediate;
+		__be32 inval_rkey;
+		__be32 pkey;
+		__be32 ft_metadata;
+	};
 	u8		rsvd40[4];
 	__be32		byte_cnt;
 	__be32		timestamp_h;