net/mlx5e: Add ToS (DSCP) header rewrite support

Add support for rewriting of DSCP part of ToS field.
Next commands, for example, can be used to offload rewrite action:

OVS:
 $ ovs-ofctl add-flow ovs-sriov "ip, in_port=REP, \
       actions=mod_nw_tos:68, output:NIC"

iproute2 (used retain mask, as tc command rewrite whole ToS field):
 $ tc filter add dev REP ingress protocol ip prio 1 flower skip_sw \
       ip_proto icmp action pedit munge ip tos set 68 retain 0xfc pipe \
       action mirred egress redirect dev NIC
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -2290,6 +2290,7 @@ static struct mlx5_fields fields[] = {
 	OFFLOAD(ETHERTYPE,  16, U16_MAX, eth.h_proto, 0, ethertype),
 	OFFLOAD(FIRST_VID,  16, U16_MAX, vlan.h_vlan_TCI, 0, first_vid),
 
+	OFFLOAD(IP_DSCP, 8,    0xfc, ip4.tos,   0, ip_dscp),
 	OFFLOAD(IP_TTL,  8,  U8_MAX, ip4.ttl,   0, ttl_hoplimit),
 	OFFLOAD(SIPV4,  32, U32_MAX, ip4.saddr, 0, src_ipv4_src_ipv6.ipv4_layout.ipv4),
 	OFFLOAD(DIPV4,  32, U32_MAX, ip4.daddr, 0, dst_ipv4_dst_ipv6.ipv4_layout.ipv4),