net/mlx5e: Use flow keys dissector to parse packets for ARFS

The current ARFS code relies on certain fields to be set in the SKB
(e.g. transport_header) and extracts IP addresses and ports by custom
code that parses the packet. The necessary SKB fields, however, are not
always set at that point, which leads to an out-of-bounds access. Use
skb_flow_dissect_flow_keys() to get the necessary information reliably,
fix the out-of-bounds access and reuse the code.

Fixes: 18c908e4 ("net/mlx5e: Add accelerated RFS support")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>