mlxsw: spectrum: Fix misuse of hard_header_len

In order to specify that the mlxsw spectrum driver needs additional
headroom for packets, there have been use of the hard_header_len field of
the netdevice struct.

This commit changes that to use needed_headroom instead, as this is the
correct way to do that.

Fixes: 56ade8fe ("mlxsw: spectrum: Add initial support for Spectrum ASIC")
Signed-off-by: NYotam Gigi <yotamg@mellanox.com>
Acked-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -2285,7 +2285,7 @@ static int mlxsw_sp_port_create(struct mlxsw_sp *mlxsw_sp, u8 local_port,
 	/* Each packet needs to have a Tx header (metadata) on top all other
 	 * headers.
 	 */
-	dev->hard_header_len += MLXSW_TXHDR_LEN;
+	dev->needed_headroom = MLXSW_TXHDR_LEN;
 
 	err = mlxsw_sp_port_system_port_mapping_set(mlxsw_sp_port);
 	if (err) {